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<!-- Creation Date :2026-05-07T11:32:03.0638+00:00 -->
<!-- Copyright (c) 2026 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage" xlink:label="us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
          <link:loc xlink:type="locator" xlink:href="icfi-20260331.xsd#icfi_CMYAcquisitionMember" xlink:label="icfi_CMYAcquisitionMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountingPoliciesAbstract" xlink:label="us-gaap_AccountingPoliciesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="icfi-20260331.xsd#icfi_PaymentsForShareRepurchasesValue" xlink:label="icfi_PaymentsForShareRepurchasesValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCurrentLiabilitiesMember" xlink:label="us-gaap_OtherCurrentLiabilitiesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="us-gaap_DisaggregationOfRevenueLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
          <link:loc xlink:type="locator" xlink:href="icfi-20260331.xsd#icfi_HealthAndSocialProgramsMember" xlink:label="icfi_HealthAndSocialProgramsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
          <link:loc xlink:type="locator" xlink:href="icfi-20260331.xsd#icfi_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember" xlink:label="icfi_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany"/>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfReceivablesLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of billed receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfReceivablesLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfReceivablesLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfReceivablesLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Receivables Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfReceivablesLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sale of receivables liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IntangibleAssetsNetExcludingGoodwillMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Intangible Assets, Net (Excluding Goodwill) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IntangibleAssetsNetExcludingGoodwillMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Intangible assets, net (excluding goodwill).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IntangibleAssetsNetExcludingGoodwillMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Intangible Assets, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Concentration Risk Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Rolling Year Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Incorporation, State or Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Incorporation State Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">December 31, 2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2030</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares issued (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position Location, Balance [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Balance Sheet Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Financial Instruments Measured at Fair Value on Recurring Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accounts Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Accounts Payable, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Excluding Current Maturities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Long-term debt - non-current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDebtInstrumentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Long-Term Debt Instruments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDebtInstrumentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Amount Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash dividend per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MaximumDeferOfCompensationSubjectToStatutoryLimitationsPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents maximum defer of compensation subject to statutory limitations percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MaximumDeferOfCompensationSubjectToStatutoryLimitationsPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Defer Of Compensation Subject To Statutory Limitations Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MaximumDeferOfCompensationSubjectToStatutoryLimitationsPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum defer of compensation subject to statutory limitations, percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating costs and expenses:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 2 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 2</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Net of Valuation Allowance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Tax Assets, Net of Valuation Allowance, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ScheduleOfOtherInformationRelatedToOperatingAndFinanceLeasesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of other information related to operating and finance leases.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ScheduleOfOtherInformationRelatedToOperatingAndFinanceLeasesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Other Information Related to Operating and Finance Leases [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ScheduleOfOtherInformationRelatedToOperatingAndFinanceLeasesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Other Information Related to Operating and Finance Leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowHedgingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Flow Hedging [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowHedgingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flow Hedging</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, authorized (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerBasisOfPricingDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Basis of Pricing [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerBasisOfPricingDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contract with Customer, Basis of Pricing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductOrServiceAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Product and Service [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductOrServiceAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Product and Service</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NetIncomeFromChangesInEstimatesRelatedToFixedPriceContracts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income From Changes in Estimates Related to Fixed Price Contracts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NetIncomeFromChangesInEstimatesRelatedToFixedPriceContracts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net income from changes in estimates related to fixed price contracts.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NetIncomeFromChangesInEstimatesRelatedToFixedPriceContracts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net income from changes in estimates related to fixed-price contracts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total future minimum lease payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total future minimum lease payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total future minimum lease payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Noncurrent Liabilities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Long-Term Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EnergyEnvironmentInfrastructureAndDisasterRecoveryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Energy, environment, infrastructure, and disaster recovery.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EnergyEnvironmentInfrastructureAndDisasterRecoveryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Energy, Environment, Infrastructure, And Disaster Recovery [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EnergyEnvironmentInfrastructureAndDisasterRecoveryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Energy, Environment, Infrastructure, and Disaster Recovery</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Rolling Year Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2030</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInUnfulfilledPerformanceObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease in Unfulfilled Performance Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInUnfulfilledPerformanceObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in unfulfilled performance obligations.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInUnfulfilledPerformanceObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reduced amount of unfulfilled performance obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCommonStockCash_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCommonStockCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends, Common Stock, Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash and Cash Equivalents, at Carrying Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding Reconciliation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average Shares:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average common shares outstanding:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Maturities of Long-Term Debt [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Future Scheduled Repayments of Debt Principal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseImpairmentLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Impairment Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseImpairmentLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Impairment related to operating lease right-of-use asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseImpairmentLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Impairment related to right-of-use operating leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SignificantSegmentExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Segment Expenses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SignificantSegmentExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Significant segment expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SignificantSegmentExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Significant segment expenses:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Goodwill Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Goodwill</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ESACAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ESAC acquisition.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ESACAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">E S A C Acquisition [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ESACAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ESAC Acquisition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Receivable Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfCashCollectionsFromCustomersOfBilledAccountReceivablePreviouslySoldToMUFGIncludingPreviousSoldReceivablesAndRemittanceOfCashCollectionsToMUFGAndCashCollectedButNotYetRemittedT_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Reconciliation of Cash Collections from Customers of Billed Account Receivable Previously Sold to MUFG Including Previous Sold Receivables and Remittance of Cash Collections to MUFG and Cash Collected But Not Yet Remitted to MUFG [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfCashCollectionsFromCustomersOfBilledAccountReceivablePreviouslySoldToMUFGIncludingPreviousSoldReceivablesAndRemittanceOfCashCollectionsToMUFGAndCashCollectedButNotYetRemittedT_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of reconciliation of cash collections from customers of billed account receivables previously sold to MUFG including previous sold receivables and remittance of cash collections to MUFG and cash collected but not yet remitted to MUFG.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfCashCollectionsFromCustomersOfBilledAccountReceivablePreviouslySoldToMUFGIncludingPreviousSoldReceivablesAndRemittanceOfCashCollectionsToMUFGAndCashCollectedButNotYetRemittedT_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Reconciliation of Cash Collections from Customers of Billed Accounts Receivable Previously Sold to MUFG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, issued (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer Benchmark [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue from Contract with Customer</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Billed receivables sold but have not yet been collected from customers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract Receivables Sold But Not Yet Collected From Customers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contract receivables sold but not yet collected from customers.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Change in contract with customer liability current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change In Contract With Customer Liability Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Change in contract liabilities - current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Long-term restricted cash included in other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Receivables, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInReceivables_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accounts receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireBusinessesGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Businesses, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireBusinessesGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash purchase price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireBusinessesGross_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Initial cash purchase price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturities, Repayments of Principal in Rolling Year Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">March 31, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">May 6, 2027 (Maturity)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromAccountsReceivableSecuritization_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Accounts Receivable Securitization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromAccountsReceivableSecuritization_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Collections from customers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromAccountsReceivableSecuritization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collections from customers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionAcquireeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionAcquireeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Business Acquisition, Acquiree</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PriorPeriodReclassificationAdjustmentDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reclassification, Comparability Adjustment [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PriorPeriodReclassificationAdjustmentDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reclassification</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFinancingReceivablesPastDueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financing Receivable, Past Due [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Amounts reclassified from accumulated other comprehensive (loss) income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amounts reclassified from accumulated other comprehensive (loss) income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Liabilities and Stockholders&#8217; Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PayablesAndAccrualsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payables and Accruals [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Employee Related Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued salaries and benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Employee Related Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">December 31, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hedging Relationship [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hedging Relationship</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expenses and Other Current Assets [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Prepaid Expenses and Other Current Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid Expenses and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LatestTaxYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Latest Tax Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LatestTaxYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Latest Tax Year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToTerminate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Option to Terminate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToTerminate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, option to terminate lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Asset Acquired to Liability Assumed, Excess (Less), and Goodwill [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statutory tax rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Goodwill</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Goodwill</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance as of December 31, 2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance as of January 1, 2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Goodwill, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Noncash Income (Expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Noncash Income (Expense), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other operating adjustments, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effective tax rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Effective tax rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfConsolidatedEBITDA_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of consolidated EBITDA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfConsolidatedEBITDA_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Consolidated EBITDA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfConsolidatedEBITDA_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of consolidated EBITDA.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid in Capital, Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LesseeOperatingAndFinanceLeaseLiabilityMaturityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lessee operating and finance lease liability maturity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LesseeOperatingAndFinanceLeaseLiabilityMaturityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating and Finance Lease Liability Maturity [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LesseeOperatingAndFinanceLeaseLiabilityMaturityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Future Minimum Lease Payments Under Non-Cancellable Operating and Finance Leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate During Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedOtherFutureLeaseRelatedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued other future lease-related expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedOtherFutureLeaseRelatedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Other Future Lease-Related Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedOtherFutureLeaseRelatedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued other future lease-related expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ShareRepurchaseProgramAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase Program [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ShareRepurchaseProgramAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Repurchase Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInAccruedSubcontractorAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase Decrease in accrued subcontractor and other direct costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInAccruedSubcontractorAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accrued Subcontractor And Other Direct Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInAccruedSubcontractorAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued subcontractors and other direct costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VestingDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vesting [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VestingDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vesting</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Share-based compensation arrangement by share-based payment award, number of shares grants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based compensation arrangement by share-based payment award, number of shares grants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation of Revenue [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disaggregation Of Revenue [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerAssetsLiabilitiesNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Change in contract with customer assets liability net current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerAssetsLiabilitiesNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change In Contract With Customer Assets Liabilities Net Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerAssetsLiabilitiesNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net contract assets (liabilities)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerAssetsLiabilitiesNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Change in net contract assets (liabilities)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Dilutive Effect of Stock Options RSUs and PSAs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_VestingOfRestrictedStockUnitsAndPerformanceShareAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vesting of RSUs and PSAs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_VestingOfRestrictedStockUnitsAndPerformanceShareAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vesting of Restricted Stock Units and Performance Share Awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_VestingOfRestrictedStockUnitsAndPerformanceShareAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Vesting of restricted stock units and performance share awards member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TrademarksAndTradeNamesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trademarks and Trade Names [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TrademarksAndTradeNamesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trade Names and Trademarks</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Basic EPS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation of Revenue [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disaggregation of Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractWithCustomerAssetsLiabilitiesNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contract with customer assets (liabilities), net current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractWithCustomerAssetsLiabilitiesNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract With Customer Assets Liabilities Net Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractWithCustomerAssetsLiabilitiesNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net contract assets (liabilities)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments of Long-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payments on working capital facilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Repayments of Long-Term Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRepurchaseOfEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Repurchase of Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRepurchaseOfEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments for Repurchase of Equity, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRepurchaseOfEquity_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payments for share repurchases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Prior year tax adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prior year tax adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ImpairmentOfLeasehold_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Impairment of Leasehold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ImpairmentOfLeasehold_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Impairment related to leasehold improvement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Current Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile net income to net cash provided by operating activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hedging Designation [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hedging Designation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date of Record</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend record date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillWrittenOffRelatedToSaleOfBusinessUnit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Goodwill, Written off Related to Sale of Business Unit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillWrittenOffRelatedToSaleOfBusinessUnit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minus: Goodwill resulting from business divestiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillWrittenOffRelatedToSaleOfBusinessUnit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: Goodwill resulting from business divestiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillWrittenOffRelatedToSaleOfBusinessUnit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: Goodwill resulting from business divestitures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillWrittenOffRelatedToSaleOfBusinessUnit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: Goodwill resulting from business divestiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ShareRepurchaseProgramDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase Program [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ShareRepurchaseProgramDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Repurchase Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfBilledContractReceivablesSoldToMufgIncludingReceivablesSoldToMufcAndCollectedFromCustomersOnBehalfOfMufgAndReceivablesNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of reconciliation of billed contract receivables sold to MUFG including receivables sold to MUFC and collected from customers on behalf of MUFG and receivables not yet collected from customers.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfBilledContractReceivablesSoldToMufgIncludingReceivablesSoldToMufcAndCollectedFromCustomersOnBehalfOfMufgAndReceivablesNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Reconciliation of Billed Contract Receivables Sold to MUFG Including Receivables Sold To MUFC And Collected from Customers On Behalf of MUFG And Receivables Not Yet Collected from Customers [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfBilledContractReceivablesSoldToMufgIncludingReceivablesSoldToMufcAndCollectedFromCustomersOnBehalfOfMufgAndReceivablesNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Reconciliation of Billed Accounts Receivable Sold to MUFG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Rule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Rule 10b51 Arr Modified Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Rule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Rule 10b51 Arr modified flag.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Rule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Rule 10b5-1 Arrangement Modified</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders&#8217; Equity:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hedging Designation [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hedging Designation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Term loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Term Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Term Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings (Accumulated Deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Retained earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Retained Earnings (Accumulated Deficit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionDescriptionOfAcquiredEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Description of Acquiree</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionDescriptionOfAcquiredEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Business acquisition, description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BasisOfPresentationAndNatureOfOperationsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Basis of presentation and nature of operations.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BasisOfPresentationAndNatureOfOperationsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis Of Presentation And Nature Of Operations [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BasisOfPresentationAndNatureOfOperationsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation and Nature of Operations [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based Compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Rolling Year Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleAndCollectionOfReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from (Payments for) Sale and Collection of Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleAndCollectionOfReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from (payments for) sale and collection of receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleAndCollectionOfReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from (payments for) sale of billed accounts receivable amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LettersOfCreditSublimit_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Letters of credit sublimit.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LettersOfCreditSublimit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letters Of Credit Sublimit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LettersOfCreditSublimit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Letters of credit sublimit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeasesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leases [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Contract with Customer, Liability, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Contract liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Contract liabilities - current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Lease, Description [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lessee Lease Description [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductsAndServicesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Product and Service [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductsAndServicesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Product and Service</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfBilledReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfBilledReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfBilledReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale Of Billed Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SaleOfBilledReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sale of billed receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DelayedDrawTermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed-Draw Term Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DelayedDrawTermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw Term Loan (DDTL) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LIABILITIES AND STOCKHOLDERS' EQUITY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Cash Used in Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmProfitLossMeasureHowUsedDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingRelationshipDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hedging Relationship [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingRelationshipDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hedging Relationship</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfBilledAccountReceivableSoldToMUFGIncludingReceivablesSoldToMUFCAndCollectedFromCustomersOnBehalfOfMUFGAndReceivablesNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Reconciliation of Billed Account Receivable Sold to MUFG Including Receivables Sold To MUFC And Collected from Customers On Behalf of MUFG And Receivables Not Yet Collected from Customers [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfBilledAccountReceivableSoldToMUFGIncludingReceivablesSoldToMUFCAndCollectedFromCustomersOnBehalfOfMUFGAndReceivablesNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of reconciliation of billed account receivable sold to MUFG including receivables sold to MUFC and collected from customers on behalf of MUFG and receivables not yet collected from customers.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfBilledAccountReceivableSoldToMUFGIncludingReceivablesSoldToMUFCAndCollectedFromCustomersOnBehalfOfMUFGAndReceivablesNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Reconciliation of Billed Accounts Receivable Sold to MUFG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notes Tables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Earnings per Share:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per share:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Information [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Disclosure of Cash Flow Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental disclosure of cash flow information:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Business combination, recognized identifiable assets acquired and liabilities assumed, working capital.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Working Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Working capital acquired</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net working capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position Location, Balance [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Balance Sheet Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMYSolutionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">C M Y Solutions, L L C.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMYSolutionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">C M Y Solutions, L L C. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMYSolutionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CMY Solutions, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditDerivativesContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Derivatives Contract Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Right-of-Use Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease - right-of-use assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total operating lease right-of-use assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, Undiscounted Excess Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Less: Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DelayedDrawTermLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw term loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DelayedDrawTermLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw Term Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DelayedDrawTermLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AmortizationOfIntangibleAssetsAcquiredInBusinessCombinationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization of Intangible Assets Acquired in Business Combinations [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AmortizationOfIntangibleAssetsAcquiredInBusinessCombinationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amortization of intangible assets acquired in business combinations.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AmortizationOfIntangibleAssetsAcquiredInBusinessCombinationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of Intangible Assets Acquired in Business Combinations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SecurityAndOtherCivilianAndCommercialMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Security and other civilian &amp; commercial.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SecurityAndOtherCivilianAndCommercialMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Security And Other Civilian And Commercial [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SecurityAndOtherCivilianAndCommercialMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Security and Other Civilian &amp; Commercial</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SecurityAndOtherCivilianAndCommercialMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security And Other Civilian And Commercial</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseOptionToTerminate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Finance Lease, Option to Terminate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseOptionToTerminate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, option to terminate lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Asset Acquired, Other Asset, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income taxes, net of refunds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Paid, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Receivable, Allowance for Credit Loss, Current</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Change in Cash, Cash Equivalents, and Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Domain]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Restricted Stock Units</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current period other comprehensive (loss) income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other comprehensive loss net of tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other comprehensive loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CostBasedContractMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cost based contract.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CostBasedContractMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cost Based Contract [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CostBasedContractMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost-Based</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseRemainingLeaseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Finance Lease, Remaining Lease Term</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Other Operating Liabilities, Total</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CreativeSystemsAndConsultingAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Creative systems and consulting acquisition.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CreativeSystemsAndConsultingAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Creative Systems and Consulting Acquisition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedTranslationAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Foreign Currency Adjustment Attributable to Parent [Member]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative [Table]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Effect of taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Notional Amount</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Fiscal Year End Date</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Long-Term Debt Instruments [Table]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Quarterly Report</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReceivablesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Receivables [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerRelationshipsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Customer Relationships [Member]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AmortizationPeriodOfPreTransitionForeignCurrencyLossesAgainstTaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization period of pre-transition foreign currency losses against taxable income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MasterReceivablesPurchaseAgreementWithMufgBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Master receivables purchase agreement with MUFG bank.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MasterReceivablesPurchaseAgreementWithMufgBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Master Receivables Purchase Agreement with MUFG Bank [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MasterReceivablesPurchaseAgreementWithMufgBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Master Receivables Purchase Agreement with MUFG Bank</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MasterReceivablesPurchaseAgreementWithMufgBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Master Receivables Purchase Agreement with MUFG Bank</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, State or Province</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CompanyOwnedLifeInsurancePoliciesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Company owned life insurance policies.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SegmentDepreciationAndAmortizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Depreciation and Amortization [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SegmentDepreciationAndAmortizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Segment depreciation and amortization.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialLiabilitiesFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Liabilities Fair Value Disclosure</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Income (Loss), Net of Tax, Attributable to Parent</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_JulyThirtyFirstTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">July thirty first two thousand thirty.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Goodwill</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Goodwill</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_RevenueFromContractWithCustomerLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revenue from contract with customer.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, after Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Stock Options Exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Exercise of stock options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AppliedEnergyGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Applied Energy Group, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AppliedEnergyGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Applied Energy Group Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AppliedEnergyGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Applied Energy Group, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OmnibusPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the Omnibus Plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OmnibusPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Omnibus Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OmnibusPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Omnibus Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PerformanceSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Performance Shares [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PerformanceSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Performance Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInDeferredIncomeTaxesAndUnrecognizedIncomeTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase (decrease) in deferred income taxes and unrecognized income tax benefits.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInDeferredIncomeTaxesAndUnrecognizedIncomeTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Deferred Income Taxes and Unrecognized Income Tax Benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInDeferredIncomeTaxesAndUnrecognizedIncomeTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Deferred income taxes and unrecognized income tax benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInDeferredIncomeTaxesAndUnrecognizedIncomeTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred income taxes and unrecognized income tax benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BilledContractReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Billed Contracts Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BilledContractReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Billed and billable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Assets, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unamortized debt issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Unamortized debt issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationFromSegmentTotalsToConsolidatedAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reconciliation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_FinanceLeasesTerminationLeaseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Finance leases, termination lease term.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_FinanceLeasesTerminationLeaseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Leases, Termination Lease Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_FinanceLeasesTerminationLeaseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, termination lease term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInOperatingLeaseAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase (decrease) in operating lease assets and liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInOperatingLeaseAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Operating Lease Assets And Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncreaseDecreaseInOperatingLeaseAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Operating lease assets and liabilities, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Finance Lease, Option to Extend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, option to extend lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AOCI Attributable to Parent [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Other Comprehensive Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_RepaymentsOfRestrictedContractFunds_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Repayments of restricted contract funds.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_RepaymentsOfRestrictedContractFunds_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments Of Restricted Contract Funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_RepaymentsOfRestrictedContractFunds_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payment of restricted contract funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finite-Lived Intangible Assets, Major Class Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finite-Lived Intangible Assets, Major Class Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Common, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury stock, shares (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Rolling Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2031</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationConsiderationTransferred1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Consideration Transferred</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationConsiderationTransferred1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase price acquisition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationConsiderationTransferred1_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Business Combination, Consideration Transferred, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Option to Extend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, option to extend lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfBonusDepreciationDomesticResearchCostExpensingAndBusinessInterestExpenseLimitationUnderOneBigBeautifulBillAct_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of bonus depreciation, domestic research cost expensing and business interest expense limitation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfBonusDepreciationDomesticResearchCostExpensingAndBusinessInterestExpenseLimitationUnderOneBigBeautifulBillAct_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Bonus Depreciation Domestic Research Cost Expensing and Business Interest Expense Limitation Under One Big Beautiful Bill Act</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfBonusDepreciationDomesticResearchCostExpensingAndBusinessInterestExpenseLimitationUnderOneBigBeautifulBillAct_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of bonus bonus depreciation domestic research cost expensing and business interest expense limitation under one big beautiful bill act.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USStateAndLocalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">US state and local government.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USStateAndLocalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S State And Local Government [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USStateAndLocalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. State and Local Government</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, par value $.001 per share; 5,000,000 shares authorized; none issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Finite-Lived</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase price allocated to intangibles</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Customer-related intangibles</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Selling, General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Indirect and selling expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Selling, General and Administrative Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturities, Repayments of Principal in Rolling Year Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">December 31, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DirectLaborAndRelatedFringeBenefitCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Direct labor and related fringe benefit costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DirectLaborAndRelatedFringeBenefitCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Direct Labor And Related Fringe Benefit Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DirectLaborAndRelatedFringeBenefitCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Direct labor &amp; related fringe benefit costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfTreasuryStockTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Treasury Stock [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfTreasuryStockTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class Of Treasury Stock [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 3 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesFairValueDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Fair Value Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesFairValueDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfCashCollectionsAndRemittancesForSaleOfBilledReceivablesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Reconciliation of Cash Collections and Remittances to MUFG for Sale of Billed Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfCashCollectionsAndRemittancesForSaleOfBilledReceivablesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Reconciliation Of Cash Collections And Remittances For Sale Of Billed Receivables [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfCashCollectionsAndRemittancesForSaleOfBilledReceivablesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of reconciliation of cash collections and remittances for sale of billed receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NumberOfOfficeFacilitiesCeasedUse_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of office facilities, ceased use.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NumberOfOfficeFacilitiesCeasedUse_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Office Facilities, Ceased Use</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NumberOfOfficeFacilitiesCeasedUse_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of office facilities, ceased use</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxPeriodDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Period [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on Sale of Interest Rate Hedge Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CashSettledRSUsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents cash settled RSUs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CashSettledRSUsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Settled R S Us [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CashSettledRSUsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Settled RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CashSettledRSUsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cash-Settled RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Receivable, after Allowance for Credit Loss, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts receivable, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts receivable, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Accounts Receivable, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Renewal Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, extendable lease term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies (Note 13)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_JuneTwentySixTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">June Twenty Six Two Thousand Thirty [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_JuneTwentySixTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">June 26, 2030</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_JuneTwentySixTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">June twenty six two thousand thirty.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillPurchaseAccountingAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Goodwill, Measurement Period Adjustment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillPurchaseAccountingAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Measurement period adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillPurchaseAccountingAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Add: Goodwill resulting from business combination</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillPurchaseAccountingAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Add: Goodwill resulting from business combinations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillPurchaseAccountingAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Goodwill resulting from business combination</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedComputerSoftwareNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capitalized Computer Software, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedComputerSoftwareNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Capitalized Computer Software, Net, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedComputerSoftwareNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Capitalized Computer Software, Net, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedComputerSoftwareNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Capitalized Computer Software, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedComputerSoftwareNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capitalized software intangible assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfGoodwillTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Goodwill [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfGoodwillTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Changes in Carrying Amount of Goodwill</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InConnectionWithVestingOfRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">In Connection with Vesting of Restricted Stock Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InConnectionWithVestingOfRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">In connection with vesting of restricted stock units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InConnectionWithVestingOfRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">In connection with vesting of restricted stock units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProvisionForOtherCreditLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Provision for Other Credit Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProvisionForOtherCreditLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Provision for credit losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Benchmark [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Concentration Risk Benchmark</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Lease, Description [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lessee Lease Description [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BilledAccountsReceivableSoldAndNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BilledAccountsReceivableSoldAndNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Billed Accounts Receivable Sold And Not Yet Collected From Customers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BilledAccountsReceivableSoldAndNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Billed accounts receivable sold and not yet collected from customers.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BilledAccountsReceivableSoldAndNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effect of Exchange Rate Changes on Cash, Cash Equivalents, and Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Income (Expense), Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Income (Expense), Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Asset Acquired, Cash and Cash Equivalent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Credit facility.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Recognized Amount [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-term Debt, Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted-average number of basic shares outstanding during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfContractReceivablesSoldButNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Contract Receivables Sold But Not Yet Collected From Customers [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfContractReceivablesSoldButNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of contract receivables sold but not yet collected from customers.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfContractReceivablesSoldButNotYetCollectedFromCustomersTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Accounts Receivable Sold to MUFG but Not Yet Collected From Customers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NonemployeeDirectOrAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-Employee Director Awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NonemployeeDirectOrAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonemployee Direct Or Awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NonemployeeDirectOrAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents share-based awards exclusive to non-employee directors.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USFederalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">US federal government.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USFederalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S Federal Government [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USFederalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. Federal Government</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effective Income Tax Rate Reconciliation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementBusinessSegmentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segments [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementBusinessSegmentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EffectiveIncomeTaxRateReconciliationUncertainTaxPosition_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation Uncertain Tax Position</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EffectiveIncomeTaxRateReconciliationUncertainTaxPosition_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Effective income tax rate reconciliation uncertain tax position.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EffectiveIncomeTaxRateReconciliationUncertainTaxPosition_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Uncertain tax position</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CommercialMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commercial.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CommercialMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commercial [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CommercialMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commercial</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Tax credits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Tax Credit, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Effective Income Tax Rate Reconciliation, Tax Credit, Percent, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding balance net of unamortized debt issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">APIC, Share-Based Payment Arrangement, Increase for Cost Recognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">APIC, Share-Based Payment Arrangement, Increase for Cost Recognition, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Stockholders&#8217; Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, par value (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis of Accounting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Existence of Option to Extend [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, existence of option to extend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Stockholders' Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseResidualValueGuaranteeDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Finance Lease, Residual Value Guarantee, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseResidualValueGuaranteeDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, residual value guarantee description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Use of Estimates, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Use of Estimates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfNonvestedShareActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Awards Granted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfNonvestedShareActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Nonvested Share Activity [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Asset Acquired, Property, Plant, and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Purchase price allocated to property and equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Common [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OCI, before Reclassifications, Net of Tax, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other comprehensive (loss) income before reclassifications</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend declaration date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarliestTaxYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earliest Tax Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarliestTaxYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earliest Tax Year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CashCollectedNotYetRemittedToPurchaserOfBilledReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash collected not yet remitted to purchaser of billed receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CashCollectedNotYetRemittedToPurchaserOfBilledReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash collected not yet remitted to purchaser of billed receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CashCollectedNotYetRemittedToPurchaserOfBilledReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash collected not yet remitted to purchaser of billed receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lease liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Accrued Liabilities [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Accrued Expenses and Other Current Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument, Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued expenses and other current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Liabilities and Other Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionEffectiveDateOfAcquisition1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Effective Date of Acquisition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionEffectiveDateOfAcquisition1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Business acquisition date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Acquired Finite-Lived Intangible Assets [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instruments and Hedging Activities Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmIndividualTitleAndPositionOrGroupOrCommitteeNameExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingOtherItemAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, Other Segment Item, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingOtherItemAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other segment expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Next Rolling 12 Months</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityLeverageRatioCovenantTemporaryIncrement_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility leverage ratio covenant temporary increment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityLeverageRatioCovenantTemporaryIncrement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Leverage Ratio Covenant Temporary Increment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityLeverageRatioCovenantTemporaryIncrement_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility leverage ratio covenant temporary increment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_FebruaryTwentyEightTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">February Twenty Eight Two Thousand Thirty [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_FebruaryTwentyEightTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">February twenty eight two thousand thirty.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_FebruaryTwentyEightTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">February 28, 2030</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfGoodsAndServicesSold_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cost of Product and Service Sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfGoodsAndServicesSold_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Direct costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfGoodsAndServicesSold_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cost of Goods and Services Sold, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Restricted Cash and Cash Equivalents, Current [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash and Cash Equivalents, Current [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">December 31, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInIncomeTaxesPayableNetOfIncomeTaxesReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Income Taxes Payable, Net of Income Taxes Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInIncomeTaxesPayableNetOfIncomeTaxesReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax receivable and payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxPeriodAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Period [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Noncurrent Assets [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Treasury Stock, Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Treasury stock, 5,910,010 and 5,520,672 shares at September 30, 2025 and December 31, 2024, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Group Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock Repurchased During Period, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchased During Period, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodShares_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Stock repurchased during period, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Non-EmployeeDirectorStockAwardsRSUSMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non-Employee Director Stock Awards RSUS [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Non-EmployeeDirectorStockAwardsRSUSMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-Employee Director Stock Awards - RSUs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Non-EmployeeDirectorStockAwardsRSUSMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-Employee Director Stock Awards - RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Reportable Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of reporting segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Number of Reportable Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Long-term debt outstanding exclusive of unamortized debt issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding Balance before debt issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilitySwingLineCommitmentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility, swing line commitment amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilitySwingLineCommitmentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Swing Line Commitment Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilitySwingLineCommitmentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilitySwingLineCommitmentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Line of credit facility, swing line commitment amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income before income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Concentration Risk Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TechnologyBasedIntangibleAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Technology-Based Intangible Assets [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TechnologyBasedIntangibleAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Developed Technology</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TechnologyBasedIntangibleAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Developed Technology</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">December 31, 2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2031</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Decrease in effective income tax rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">IRC 987 regulations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders' Equity Note [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TwoHundredMillionShareRepurchaseProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">$200 Million Share Repurchase Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TwoHundredMillionShareRepurchaseProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Hundred Million Share Repurchase Program [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TwoHundredMillionShareRepurchaseProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two hundred million share repurchase program.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total of cash, cash equivalents, and restricted cash shown in the consolidated statements of cash flows</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Paid, Excluding Capitalized Interest, Operating Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Current Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Stock-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OperatingLeaseLiabilityAndFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating lease liability and finance lease liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OperatingLeaseLiabilityAndFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Operating lease liability and finance lease liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OperatingLeaseLiabilityAndFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OperatingLeaseLiabilityAndFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated useful lives of acquired intangible assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted average amortization period for intangibles</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Stock Units (RSUs) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted Stock Units (RSUs)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Restricted Stock Awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityLeverageRatioCovenant_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the maximum leverage ratio under the line of credit facility covenant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityLeverageRatioCovenant_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Leverage Ratio Covenant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityLeverageRatioCovenant_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, leverage ratio covenant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfOptionToTerminate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Existence of Option to Terminate [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfOptionToTerminate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, existence of option to terminate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncomeTaxesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Income taxes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncomeTaxesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncomeTaxesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Security, Excluded EPS Calculation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VestingAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vesting [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VestingAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vesting</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current period other comprehensive (loss) income:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current period other comprehensive income (loss):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InitialPerformanceVestingPeriodMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information relating to an initial performance vesting period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InitialPerformanceVestingPeriodMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Initial Performance Vesting Period [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InitialPerformanceVestingPeriodMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Initial Performance Vesting Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Unused Borrowing Capacity, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unused borrowing capacity amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsRSUsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock Awards RSUs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsRSUsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employee stock awards RSUs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsRSUsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Stock Awards - RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseRenewalTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Finance Lease, Renewal Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseRenewalTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, extendable lease term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BlantonAndAssociatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Blanton and Associates [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BlantonAndAssociatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Blanton and Associates [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BlantonAndAssociatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Blanton and Associates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BlantonAndAssociatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Blanton &amp; Associates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BlantonAndAssociatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Blanton &amp; Associates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Restricted Cash, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfAccountsReceivableSecuritization_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments of Accounts Receivable Securitization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfAccountsReceivableSecuritization_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Remittances to MUFG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted-average number of diluted shares outstanding during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Securities Act File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividendsCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments of Ordinary Dividends, Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividendsCommonStock_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationOtherReconcilingItemsPercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationOtherReconcilingItemsPercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Other Reconciling Items, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cover [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense and Other Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid expenses and other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Liability Assumed, Other Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, after Rolling Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_RevenueFromContractWithCustomerTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revenue from contract with customer.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_RevenueFromContractWithCustomerTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue From Contract With Customer [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_RevenueFromContractWithCustomerTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue From Contract With Customer [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Operating Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of operating segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Number of Operating Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PaymentsForShareRepurchasesShares_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payments for share repurchases (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PaymentsForShareRepurchasesShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments For Share Repurchases Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PaymentsForShareRepurchasesShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments for share repurchases shares.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Expects to reclassify unrealized losses related to change in fair value of interest rate hedge agreement from accumulated other comprehensive (loss) income into earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net income recognized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Income, Revenue Recognized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StandbyLettersOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Standby Letters of Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StandbyLettersOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Standby Letters of Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Liability Assumed, Accounts Payable, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Interest Rate During Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate on credit facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Goodwill [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Goodwill</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recent Accounting Pronouncements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contract liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Contract liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Contract liabilities - current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based compensation arrangement by share-based payment award, award vesting period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Performance based share awards, performance period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNoteTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Income (Loss) Note [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNoteTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Other Comprehensive Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, outstanding (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Shares, Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Shares, Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NonEmployeeDirectorStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-Employee Director Stock Awards member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NonEmployeeDirectorStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non-Employee Director Stock Awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NonEmployeeDirectorStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-Employee Director Stock Awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation, Depletion and Amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Depreciation and amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Depreciation, Depletion and Amortization, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue, Remaining Performance Obligation, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unfulfilled performance obligation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total operating costs and expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReceivableTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Receivable [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeasesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Leases [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeasesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Cash Flows [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Fair Value Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-Based Payment Arrangement, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity-based compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Interest Rate Swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts and Financing Receivables [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock [Text Block]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfCashCollectionsFromCustomersOfBilledContractReceivablesPreviouslySoldToMufgIncludingPreviousSoldReceivablesAndRemittanceOfCashCollectionsToMufgAndCashCollectedButNotYetRemitte_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Reconciliation of Cash Collections from Customers of Billed Contract Receivables Previously Sold to MUFG Including Previous Sold Receivables and Remittance of Cash Collections to MUFG and Cash Collected But Not Yet Remitted to MUFG [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SummaryOfReconciliationOfCashCollectionsFromCustomersOfBilledContractReceivablesPreviouslySoldToMufgIncludingPreviousSoldReceivablesAndRemittanceOfCashCollectionsToMufgAndCashCollectedButNotYetRemitte_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Reconciliation of Cash Collections from Customers of Billed Accounts Receivable Previously Sold to MUFG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DeferredCompensationPlanLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred compensation plan liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DeferredCompensationPlanLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Compensation Plan Liabilities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DeferredCompensationPlanLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred Compensation Plan Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturities, Repayments of Principal in Rolling Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">May 6, 2027 (Maturity)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Cash-SettledRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash-Settled Restricted Stock Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Cash-SettledRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash-settledrestrictedstockunits.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_Cash-SettledRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash-Settled RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Receivable, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other financing, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from (Payment for) Other Financing Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Intangible Assets, Net (Excluding Goodwill)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other intangible assets, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Intangible Assets, Net (Excluding Goodwill), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change In Contract With Customer Liability Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Change in contract with customer liability noncurrent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in Other long-term liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Change in Contract liabilities - non-current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDivestitureOfBusinesses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Divestiture of Businesses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDivestitureOfBusinesses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from divestiture of a business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASSETS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncomeTaxesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Income taxes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncomeTaxesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_IncomeTaxesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Prepaid Expense and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expenses and other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ScheduleOfAcquisitionAndDivestitureTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of acquisition and divestiture.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ScheduleOfAcquisitionAndDivestitureTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Acquisition And Divestiture [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ScheduleOfAcquisitionAndDivestitureTable_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Schedule of Acquisition and Divestiture [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LettersOfCreditGuarantees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Letters of credit guarantees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LettersOfCreditGuarantees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letters of credit guarantees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LettersOfCreditGuarantees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Letters of credit guarantees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Components of Accumulated Other Comprehensive Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Benchmark [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Concentration Risk Benchmark</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected period to satisfy performance obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts Payable, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseNonoperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense, Nonoperating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseNonoperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Expense, Nonoperating, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseNonoperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SemanticBitsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SemanticBits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SemanticBitsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">SemanticBits, LLC .</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SemanticBitsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Semantic Bits L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SemanticBitsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">SemanticBits LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SemanticBitsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SemanticBits LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Contract End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Disposition of Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Gain on divestiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfBusiness_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gain on divestiture of a business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on divestiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetAndLiabilityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetAndLiabilityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Contract Assets and Liabilities and Changes in Contract Balances</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective income tax rate reconciliation return to provision adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Effective income tax rate reconciliation return to provision adjustments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Return to provision adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BilledContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Billed contract receivables sold but not yet collected from customers.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BilledContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Billed Contract Receivables Sold But Not Yet Collected From Customers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BilledContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BilledContractReceivablesSoldButNotYetCollectedFromCustomers_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Asset, after Allowance for Credit Loss, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contract assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Contract assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Contract with Customer, Asset, after Allowance for Credit Loss, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionProFormaInformationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Pro Forma Information [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionProFormaInformationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Unaudited Condensed Pro Forma Financial Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionProFormaInformationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Schedule of Unaudited Condensed Pro Forma Financial Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Unrecognized compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-Based Compensation Unrecognized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Assets, Fair Value Disclosure, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskPercentage1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk, Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskPercentage1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue from clients, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NumberOfOpenStandbyLettersOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of open standby letters of credit.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NumberOfOpenStandbyLettersOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Open Standby Letters Of Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_NumberOfOpenStandbyLettersOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of open standby letters of credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employee stock awards member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock Awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Stock Awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Investing Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Cash Used in Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of each class</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Segment Reporting Information, by Segment [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Change in contract with customer assets net current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change In Contract With Customer Asset Net Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ChangeInContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Change in contract assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FederalFundsEffectiveSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fed Funds Effective Rate Overnight Index Swap Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FederalFundsEffectiveSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fed Funds Effective Rate Overnight Index Swap Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FederalFundsEffectiveSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Federal Funds Open Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Instruments and Hedging Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instruments and Hedging Activities Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedExpensesAndOtherCurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued expenses and other current liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedExpensesAndOtherCurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Expenses And Other Current Liabilities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedExpensesAndOtherCurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued Expenses and Other Current Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Liabilities, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other long-term liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in operating assets and liabilities, net of the effects of acquisitions:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in operating assets and liabilities, net of the effect of acquisitions:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LettersOfCreditOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letters of Credit Outstanding, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LettersOfCreditOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Letters of credit outstanding, amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LettersOfCreditOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Letters of credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring and Nonrecurring [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Acquisitions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid-in Capital [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional Paid-in Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued expenses and other current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpensesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Accrued Expenses and Other Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpensesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpensesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Business combination recognized identifiable assets acquired and liabilities assumed, accrued expenses and other liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpensesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Accrued expenses and other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock repurchase program, authorized amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase Program, Authorized, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OpenTaxYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Open Tax Year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OpenTaxYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Open tax year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued salaries and benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee-related Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Employee-related Liabilities, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Financing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value, Recurring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable and Accrued Liabilities Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued Expenses and Other Current Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total future minimum lease payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, Undiscounted Excess Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromRestrictedContractFunds_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Restricted Contract Funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromRestrictedContractFunds_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Receipt of restricted contract funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromRestrictedContractFunds_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from restricted contract funds.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Components</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Components [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityAdditionalRevolvingCreditCommitmentsUnderExistingLoanFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of Credit Facility Additional Revolving Credit Commitments Under Existing Loan Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityAdditionalRevolvingCreditCommitmentsUnderExistingLoanFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Additional Revolving Credit Commitments Under Existing Loan Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LineOfCreditFacilityAdditionalRevolvingCreditCommitmentsUnderExistingLoanFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, additional revolving credit commitments under existing loan facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Component</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Goodwill and Intangible Assets Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationOfRevenueFromSegmentsToConsolidatedTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reconciliation of Revenue from Segments to Consolidated [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationOfRevenueFromSegmentsToConsolidatedTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Segment Revenue, Significant Segment Expenses, and Segment Profit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DeferredCompensationInvestmentsInCashSurrenderLifeInsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred compensation investments in cash surrender life insurance.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DeferredCompensationInvestmentsInCashSurrenderLifeInsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Compensation Investments In Cash Surrender Life Insurance [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DeferredCompensationInvestmentsInCashSurrenderLifeInsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred Compensation Investments in Cash Surrender Life Insurance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Summary of Preliminary Purchase Price Allocation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Asset Acquired and Liability Assumed [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Purchase Price Allocation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Business Acquisition</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of shares pursuant to vesting of restricted stock units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerBasisOfPricingAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Basis of Pricing [Axis]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Depreciation, Depletion and Amortization, Nonproduction, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Depreciation and amortization expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contract receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract Receivables [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend payment date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Designated as Hedging Instrument [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Designated as Hedging Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Liability, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other long-term liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Contract liabilities - non-current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock, par value $.001; 70,000,000 shares authorized; 24,336,393 and 24,186,962 shares issued at June 30, 2025 and December 31, 2024, respectively; 18,428,490 and 18,666,290 shares outstanding at June 30, 2025 and December 31, 2024, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, par value $.001; 70,000,000 shares authorized;24,513,156 and 24,378,749 shares issued at March 31, 2026 and December 31, 2025 respectively; 18,117,062 and 18,247,837 shares outstanding at March 31, 2026 and December 31, 2025, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFixedInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFixedInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Derivative fixed interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFixedInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative fixed interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturities, Repayments of Principal in Rolling Year Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">May 6, 2027 (Maturity)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">December 31, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CommercialMarketingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commercial marketing.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CommercialMarketingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commercial Marketing Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CommercialMarketingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Commercial Marketing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CommercialMarketingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commercial Marketing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInCommodityContractAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Commodity Contract Assets and Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInCommodityContractAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net contract assets and liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledReceivablesNotYetRemitted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from (Payments for) Sale of Billed Receivables Not Yet Remitted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledReceivablesNotYetRemitted_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from (payments for) sale of billed receivables not yet remitted.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledReceivablesNotYetRemitted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from (payments for) sale of billed receivables but not yet remitted to MUFG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contract assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business combination recognized identifiable assets acquired and liabilities assumed contract assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Business combination recognized identifiable assets acquired and liabilities assumed contract assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Contract assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_JamesMorganMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">James Morgan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_JamesMorganMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">James Morgan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_JamesMorganMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">James Morgan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">State taxes, net of federal benefit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseResidualValueGuaranteeDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Residual Value Guarantee, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseResidualValueGuaranteeDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, residual value guarantee description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares authorized (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USStateAndInternationalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">US state and international government.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USStateAndInternationalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S State And International Government [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_USStateAndInternationalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Government</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finite-Lived Intangible Assets by Major Class [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finite-Lived Intangible Assets by Major Class</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MergersAcquisitionsAndDispositionsDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mergers, Acquisitions and Dispositions Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MergersAcquisitionsAndDispositionsDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Acquisition and Divestiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MergersAcquisitionsAndDispositionsDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Acquisitions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lender Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lender Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsNotesAndLoansReceivableLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts, Notes, Loans and Financing Receivable [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Business Acquisitions By Acquisition [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-term debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerConcentrationRiskMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Customer Concentration Risk [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerConcentrationRiskMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Customer Concentration Risk</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Nonoperating Income (Expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Nonoperating Income (Expense), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other income (expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income (expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Other Comprehensive Income (Loss) [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Other Comprehensive Income Loss [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Provision for income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income tax expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireProductiveAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payments for purchase of property and equipment and capitalized software</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireProductiveAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Productive Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireProductiveAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments to Acquire Productive Assets, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireProductiveAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Pa</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchased During Period, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock Repurchased During Period, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Share repurchase amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Remaining Lease Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, remaining lease term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LesseeOperatingLeaseTerminationTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lessee operating lease termination term.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LesseeOperatingLeaseTerminationTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Termination Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LesseeOperatingLeaseTerminationTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, termination lease term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Other Comprehensive Income (Loss), Net of Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated other comprehensive loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accumulated Other Comprehensive Income (Loss), Net of Tax, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other investing, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment for (Proceeds from) Other Investing Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other investing, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Number of shares, granted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Awards Granted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restrictions on Cash and Cash Equivalents [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reconciliation of Cash and Cash Equivalents, and Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableSale_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Receivable, Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableSale_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Billed accounts receivable sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financing Receivable, Past Due [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash deferred income tax expense (benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total deferred</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_VestingOfRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Vesting of Restricted Stock Units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_VestingOfRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vesting of Restricted Stock Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_VestingOfRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vesting of RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combinations [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Diluted EPS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditDerivativesByContractTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Derivatives Contract Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation of Revenue [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DerivativeAverageFixedInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative average interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DerivativeAverageFixedInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Average Fixed Interest Rate During Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DerivativeAverageFixedInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative average fixed interest rate during period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BasisOfPresentationAndNatureOfOperationsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis Of Presentation And Nature Of Operations [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BasisOfPresentationAndNatureOfOperationsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Basis of presentation and nature of operations.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_BasisOfPresentationAndNatureOfOperationsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis Of Presentation And Nature Of Operations [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, maximum borrowing capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromOtherShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Other Short-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromOtherShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from other short-term borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Liabilities Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lease liabilities current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease liabilities - current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedSubcontractorAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents accrued subcontractor and other direct costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedSubcontractorAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Subcontractor And Other Direct Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccruedSubcontractorAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued subcontractors and other direct costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FixedPriceContractMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fixed-Price Contract [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FixedPriceContractMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fixed-Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting Information [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Group Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and Equipment, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total property and equipment, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Issuance of shares pursuant to vesting of restricted stock units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of shares pursuant to employee stock purchase plan and vesting of restricted stock units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromBankDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Bank Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromBankDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Advances from working capital facilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash, Cash Equivalents, and Restricted Cash, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash, Cash Equivalents, and Restricted Cash, Beginning of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DelayedDrawTermLoanFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw term loan facility.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DelayedDrawTermLoanFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw Term Loan Facility [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_DelayedDrawTermLoanFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw Term Loan Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Income (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Operating income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillForeignCurrencyTranslationGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Goodwill, Foreign Currency Translation, Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillForeignCurrencyTranslationGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effect of foreign currency translation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfResidualValueGuarantee_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Existence of Residual Value Guarantee [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfResidualValueGuarantee_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, existence of residual value guarantee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Retained Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfOtherShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments of Other Short-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfOtherShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayments of other short-term borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InternationalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">International Government [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InternationalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">International Government</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_InternationalGovernmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">International government.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Noncash Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash equity compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Share-Based Payment Arrangement, Noncash Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsPSAsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Stock Awards - PSAs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsPSAsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock Awards PSAs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_EmployeeStockAwardsPSAsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employee stock awards PSAs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SecuredOvernightFinancingRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Secured Overnight Financing Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SecuredOvernightFinancingRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Secured Overnight Financing Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SecuredOvernightFinancingRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Secured Overnight Financing Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 1 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Cash Provided by Financing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease, Cost [Table Text Block]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerRelatedIntangibleAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Customer-Related Intangible Assets [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerRelatedIntangibleAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Customer-Related Intangible Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerRelatedIntangibleAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Customer-Related Intangibles</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SubcontractorsAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subcontractors And Other Direct Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SubcontractorsAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Subcontractors and other direct costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_SubcontractorsAndOtherDirectCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subcontractors and other direct costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DevelopedTechnologyRightsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Developed Technology Rights [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DevelopedTechnologyRightsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Developed Technology</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DevelopedTechnologyRightsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Developed Technology</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Income Tax Liabilities, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Contract [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfGoodwillTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Goodwill [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfGoodwillTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Goodwill [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledContractReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from (Payments for) Sale of Billed Contract Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledContractReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from (payments for) sale of billed contract receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledContractReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from (payments for) sale of billed contract receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledContractReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Proceeds from (Payments for) Sale of Billed Contract Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Recognized Asset Acquired, Receivable, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledAccountReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From (Payments For) Sale Of Billed Account Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledAccountReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from (payments for) sale of billed account receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ProceedsFromPaymentsForSaleOfBilledAccountReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from (Payments for) Sale of Billed accounts Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Weighted Average Shares Excluded from Calculation of EPS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MillionShareRepurchaseProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">300.0 Million Share Repurchase Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MillionShareRepurchaseProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">300.0 Million Share Repurchase Program [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_MillionShareRepurchaseProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">300.0 million share repurchase program member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contract receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_ContractReceivablesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract Receivables [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMGAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">C M G acquisition.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMGAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">C M G acquisition [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMGAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">C M G acquisition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfBonusDepreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Bonus Depreciation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfBonusDepreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of bonus depreciation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PercentageOfBonusDepreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of bonus depreciation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxAssetsAndLiabilitiesExpectedToReverseInFuture_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tax cuts and jobs act of 2017 complete accounting change in tax rate deferred tax assets and liabilities expected to reverse in future.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxAssetsAndLiabilitiesExpectedToReverseInFuture_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Cuts And Jobs Act Of2017 Complete Accounting Change In Tax Rate Deferred Tax Assets And Liabilities Expected To Reverse In Future</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxAssetsAndLiabilitiesExpectedToReverseInFuture_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax assets and liabilities income tax rate expected to reverse in future</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfTreasuryStockByClassTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Treasury Stock [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfTreasuryStockByClassTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Repurchases of Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockDividendsPerShareDeclared_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Dividends, Per Share, Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockDividendsPerShareDeclared_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash dividends declared per common share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturities, Repayments of Principal in Next Rolling 12 Months</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">December 31, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">September 30, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-term Debt, Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LoansNotesTradeAndOtherReceivablesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loans, Notes, Trade and Other Receivables Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LoansNotesTradeAndOtherReceivablesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts Receivable, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OtherReceivablesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OtherReceivablesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Receivables [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_OtherReceivablesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Other Comprehensive Income (Loss) [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Other Comprehensive Income Loss [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilitiesNon-Current_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Liabilities Non-current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilitiesNon-Current_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lease liabilities non-current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_LeaseLiabilitiesNon-Current_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease liabilities - non-current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">December 31, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 31, 2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue, remaining performance obligation, percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue, Remaining Performance Obligation, Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMYAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">C M Y acquisition [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMYAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CMY Acquisition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_CMYAcquisitionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CMY acquisition.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingPoliciesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Policies [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PaymentsForShareRepurchasesValue_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payments for share repurchases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PaymentsForShareRepurchasesValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments for share repurchases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PaymentsForShareRepurchasesValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments For Share Repurchases Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_PaymentsForShareRepurchasesValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments for share repurchases value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Current Liabilities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued salaries and benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation of Revenue [Line Items]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer, Excluding Assessed Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Revenue from clients</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_HealthAndSocialProgramsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Health and social programs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_HealthAndSocialProgramsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Health And Social Programs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_HealthAndSocialProgramsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Health and Social Programs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based compensation arrangement by share-based payment award, number of shares available for grant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accumulated other comprehensive income loss cumulative changes in fair value on derivative designated from cash flow Hedges effect net of tax.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Other Comprehensive Income Loss Cumulative Changes In Fair Value On Derivative Designated From Cash Flow Hedges Effect Net Of Tax [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in Fair Value of Interest Rate Hedge Agreements and Other Adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="icfi_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Changes in Fair Value of Interest Rate Hedge Agreements</link:label>
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  <xsd:element id="icfi_LeaseLiabilities" name="LeaseLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_ChangeInContractWithCustomerAssetsLiabilitiesNetCurrent" name="ChangeInContractWithCustomerAssetsLiabilitiesNetCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_BilledContractReceivablesSoldButNotYetCollectedFromCustomers" name="BilledContractReceivablesSoldButNotYetCollectedFromCustomers" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_LettersOfCreditGuarantees" name="LettersOfCreditGuarantees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_MaximumDeferOfCompensationSubjectToStatutoryLimitationsPercentage" name="MaximumDeferOfCompensationSubjectToStatutoryLimitationsPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_DelayedDrawTermLoanFacilityMember" name="DelayedDrawTermLoanFacilityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_LineOfCreditFacilityLeverageRatioCovenantTemporaryIncrement" name="LineOfCreditFacilityLeverageRatioCovenantTemporaryIncrement" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="icfi_CMGAcquisitionMember" name="CMGAcquisitionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_DirectLaborAndRelatedFringeBenefitCosts" name="DirectLaborAndRelatedFringeBenefitCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_InConnectionWithVestingOfRestrictedStockUnitsMember" name="InConnectionWithVestingOfRestrictedStockUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_LeaseLiabilitiesCurrent" name="LeaseLiabilitiesCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_BlantonAndAssociatesMember" name="BlantonAndAssociatesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_DerivativeAverageFixedInterestRateDuringPeriod" name="DerivativeAverageFixedInterestRateDuringPeriod" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_ProceedsFromRestrictedContractFunds" name="ProceedsFromRestrictedContractFunds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_LineOfCreditFacilityAdditionalRevolvingCreditCommitmentsUnderExistingLoanFacility" name="LineOfCreditFacilityAdditionalRevolvingCreditCommitmentsUnderExistingLoanFacility" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_SummaryOfReconciliationOfCashCollectionsFromCustomersOfBilledContractReceivablesPreviouslySoldToMufgIncludingPreviousSoldReceivablesAndRemittanceOfCashCollectionsToMufgAndCashCollectedButNotYetRemitte" name="SummaryOfReconciliationOfCashCollectionsFromCustomersOfBilledContractReceivablesPreviouslySoldToMufgIncludingPreviousSoldReceivablesAndRemittanceOfCashCollectionsToMufgAndCashCollectedButNotYetRemitte" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_EmployeeStockAwardsPSAsMember" name="EmployeeStockAwardsPSAsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpensesAndOtherLiabilities" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpensesAndOtherLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_CompanyOwnedLifeInsurancePoliciesMember" name="CompanyOwnedLifeInsurancePoliciesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_ChangeInContractWithCustomerLiabilityCurrent" name="ChangeInContractWithCustomerLiabilityCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_AmortizationPeriodOfPreTransitionForeignCurrencyLossesAgainstTaxableIncome" name="AmortizationPeriodOfPreTransitionForeignCurrencyLossesAgainstTaxableIncome" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_PaymentsForShareRepurchasesShares" name="PaymentsForShareRepurchasesShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_CostBasedContractMember" name="CostBasedContractMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_JamesMorganMember" name="JamesMorganMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_CMYSolutionsLLCMember" name="CMYSolutionsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_USFederalGovernmentMember" name="USFederalGovernmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_SubcontractorsAndOtherDirectCosts" name="SubcontractorsAndOtherDirectCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_SummaryOfContractReceivablesSoldButNotYetCollectedFromCustomersTableTextBlock" name="SummaryOfContractReceivablesSoldButNotYetCollectedFromCustomersTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_IncomeTaxesLineItems" name="IncomeTaxesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_SignificantSegmentExpensesAbstract" name="SignificantSegmentExpensesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_Cash-SettledRestrictedStockUnitsMember" name="Cash-SettledRestrictedStockUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_PercentageOfBonusDepreciationDomesticResearchCostExpensingAndBusinessInterestExpenseLimitationUnderOneBigBeautifulBillAct" name="PercentageOfBonusDepreciationDomesticResearchCostExpensingAndBusinessInterestExpenseLimitationUnderOneBigBeautifulBillAct" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_SaleOfReceivablesLiabilities" name="SaleOfReceivablesLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_ContractReceivablesDomain" name="ContractReceivablesDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_JulyThirtyFirstTwoThousandThirtyMember" name="JulyThirtyFirstTwoThousandThirtyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_PercentageOfBonusDepreciation" name="PercentageOfBonusDepreciation" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_CashSettledRSUsMember" name="CashSettledRSUsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_LineOfCreditFacilitySwingLineCommitmentAmount" name="LineOfCreditFacilitySwingLineCommitmentAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_NonEmployeeDirectorStockAwardsMember" name="NonEmployeeDirectorStockAwardsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_IncreaseDecreaseInDeferredIncomeTaxesAndUnrecognizedIncomeTaxBenefits" name="IncreaseDecreaseInDeferredIncomeTaxesAndUnrecognizedIncomeTaxBenefits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_IncreaseDecreaseInUnfulfilledPerformanceObligations" name="IncreaseDecreaseInUnfulfilledPerformanceObligations" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_LesseeOperatingLeaseTerminationTerm" name="LesseeOperatingLeaseTerminationTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_ProceedsFromPaymentsForSaleAndCollectionOfReceivables" name="ProceedsFromPaymentsForSaleAndCollectionOfReceivables" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_AmortizationOfIntangibleAssetsAcquiredInBusinessCombinationsMember" name="AmortizationOfIntangibleAssetsAcquiredInBusinessCombinationsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_IncomeTaxesTable" name="IncomeTaxesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_ScheduleOfAcquisitionAndDivestitureTable" name="ScheduleOfAcquisitionAndDivestitureTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_LineOfCreditFacilityLeverageRatioCovenant" name="LineOfCreditFacilityLeverageRatioCovenant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="icfi_CommercialMember" name="CommercialMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_OperatingLeaseLiabilityAndFinanceLeaseLiability" name="OperatingLeaseLiabilityAndFinanceLeaseLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_NumberOfOpenStandbyLettersOfCredit" name="NumberOfOpenStandbyLettersOfCredit" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="icfi_IntangibleAssetsNetExcludingGoodwillMember" name="IntangibleAssetsNetExcludingGoodwillMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_MasterReceivablesPurchaseAgreementWithMufgBankMember" name="MasterReceivablesPurchaseAgreementWithMufgBankMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember" name="AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustments" name="EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustments" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_LesseeOperatingAndFinanceLeaseLiabilityMaturityTableTextBlock" name="LesseeOperatingAndFinanceLeaseLiabilityMaturityTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxAssetsAndLiabilitiesExpectedToReverseInFuture" name="TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxAssetsAndLiabilitiesExpectedToReverseInFuture" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_EnergyEnvironmentInfrastructureAndDisasterRecoveryMember" name="EnergyEnvironmentInfrastructureAndDisasterRecoveryMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_SaleOfBilledReceivables" name="SaleOfBilledReceivables" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_SummaryOfReconciliationOfBilledAccountReceivableSoldToMUFGIncludingReceivablesSoldToMUFCAndCollectedFromCustomersOnBehalfOfMUFGAndReceivablesNotYetCollectedFromCustomersTableTextBlock" name="SummaryOfReconciliationOfBilledAccountReceivableSoldToMUFGIncludingReceivablesSoldToMUFCAndCollectedFromCustomersOnBehalfOfMUFGAndReceivablesNotYetCollectedFromCustomersTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_Non-EmployeeDirectorStockAwardsRSUSMember" name="Non-EmployeeDirectorStockAwardsRSUSMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_RevenueFromContractWithCustomerLineItems" name="RevenueFromContractWithCustomerLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_RepaymentsOfRestrictedContractFunds" name="RepaymentsOfRestrictedContractFunds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_CommercialMarketingMember" name="CommercialMarketingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_CreativeSystemsAndConsultingAcquisitionMember" name="CreativeSystemsAndConsultingAcquisitionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_IncreaseDecreaseInOperatingLeaseAssetsAndLiabilities" name="IncreaseDecreaseInOperatingLeaseAssetsAndLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_CMYAcquisitionMember" name="CMYAcquisitionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_BasisOfPresentationAndNatureOfOperationsTable" name="BasisOfPresentationAndNatureOfOperationsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_NumberOfOfficeFacilitiesCeasedUse" name="NumberOfOfficeFacilitiesCeasedUse" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_SummaryOfReconciliationOfCashCollectionsAndRemittancesForSaleOfBilledReceivablesTableTextBlock" name="SummaryOfReconciliationOfCashCollectionsAndRemittancesForSaleOfBilledReceivablesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="icfi_USStateAndInternationalGovernmentMember" name="USStateAndInternationalGovernmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_SegmentDepreciationAndAmortizationMember" name="SegmentDepreciationAndAmortizationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_AppliedEnergyGroupIncMember" name="AppliedEnergyGroupIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_EmployeeStockAwardsMember" name="EmployeeStockAwardsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_InternationalGovernmentMember" name="InternationalGovernmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_TermLoanMember" name="TermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_PercentageOfConsolidatedEBITDA" name="PercentageOfConsolidatedEBITDA" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="icfi_InitialPerformanceVestingPeriodMember" name="InitialPerformanceVestingPeriodMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_OmnibusPlanMember" name="OmnibusPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_ProceedsFromPaymentsForSaleOfBilledAccountReceivables" name="ProceedsFromPaymentsForSaleOfBilledAccountReceivables" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="icfi_DeferredCompensationPlanLiabilitiesMember" name="DeferredCompensationPlanLiabilitiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_MillionShareRepurchaseProgramMember" name="MillionShareRepurchaseProgramMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_BilledAccountsReceivableSoldAndNotYetCollectedFromCustomers" name="BilledAccountsReceivableSoldAndNotYetCollectedFromCustomers" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_JuneTwentySixTwoThousandThirtyMember" name="JuneTwentySixTwoThousandThirtyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="icfi_ContractReceivablesSoldButNotYetCollectedFromCustomers" name="ContractReceivablesSoldButNotYetCollectedFromCustomers" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="icfi_RevenueFromContractWithCustomerTable" name="RevenueFromContractWithCustomerTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
</xsd:schema>
