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<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2020-02-27T23:21:12.0388337+00:00 -->
<!-- Version            : 5.0.1.321 -->
<!-- Package ID         : 565dcc1c37ce4cf59a6fd01364abc3e4 -->
<!-- Copyright (c) 2020 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="icfi_RevenueFromContractWithCustomerLineItems" name="RevenueFromContractWithCustomerLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_RevenueFromContractWithCustomerTable" name="RevenueFromContractWithCustomerTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_InterestRateSwapTwoPointEightFiveOneZeroPercentMember" name="InterestRateSwapTwoPointEightFiveOneZeroPercentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_DeferredTaxAssetsForeignDeferredIncome" name="DeferredTaxAssetsForeignDeferredIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="icfi_DeferredTaxAssetsAccruedLiabilitiesAndOtherNoncurrent" name="DeferredTaxAssetsAccruedLiabilitiesAndOtherNoncurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="icfi_DeferredTaxLiabilitiesRetentionCurrent" name="DeferredTaxLiabilitiesRetentionCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_DeferredTaxLiabilitiesPayrollTaxes" name="DeferredTaxLiabilitiesPayrollTaxes" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_DeferredTaxLiabilitiesUnbilledRevenue" name="DeferredTaxLiabilitiesUnbilledRevenue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_DeferredTaxLiabilitiesOtherCurrent" name="DeferredTaxLiabilitiesOtherCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_IncomeTaxesLineItems" name="IncomeTaxesLineItems" type="xbrli:stringItemType" 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_StateAndForeignJurisdictionsMember" name="StateAndForeignJurisdictionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxAssetsAndLiabilitiesExpectedToReverseInFuture" name="TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxAssetsAndLiabilitiesExpectedToReverseInFuture" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxProvisionalIncomeTaxExpenseBenefitIncludingAdjustmentsToValuationAllowances" name="TaxCutsAndJobsActOf2017CompleteAccountingChangeInTaxRateDeferredTaxProvisionalIncomeTaxExpenseBenefitIncludingAdjustmentsToValuationAllowances" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="icfi_TaxCutsAndJobsActOf2017CompleteAccountingChangeInValuationAllowancesForCumulativeForiegnTaxCreditCarryForward" name="TaxCutsAndJobsActOf2017CompleteAccountingChangeInValuationAllowancesForCumulativeForiegnTaxCreditCarryForward" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_TaxCutsAndJobsActOf2017CompleteAccountingChangeInCumulativeForeignTaxCreditCarryForward" name="TaxCutsAndJobsActOf2017CompleteAccountingChangeInCumulativeForeignTaxCreditCarryForward" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="icfi_IncomeTaxesProvidedForAdditionalOutsideBasisDifferenceInherentInEntitiesAsResultOfReinvestment" name="IncomeTaxesProvidedForAdditionalOutsideBasisDifferenceInherentInEntitiesAsResultOfReinvestment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="icfi_OperatingLossCarryforwardsExpirationYear" name="OperatingLossCarryforwardsExpirationYear" type="xbrli:gYearItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_OperatingLossCarryforwardsExpirationTerm" name="OperatingLossCarryforwardsExpirationTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_TaxCreditCarryforwardExpirationYear" name="TaxCreditCarryforwardExpirationYear" type="xbrli:gYearItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_StockholdersEquityAdjustedBalance" name="StockholdersEquityAdjustedBalance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember" name="AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInFairValueOnDerivativeDesignatedFromCashFlowHedgesEffectNetOfTaxMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_OmnibusPlanMember" name="OmnibusPlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_NonemployeeDirectOrAwardsMember" name="NonemployeeDirectOrAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedForfeitureRate" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedForfeitureRate" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PriceRange1Member" name="PriceRange1Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_PriceRange2Member" name="PriceRange2Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_PriceRange3Member" name="PriceRange3Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_PriceRange4Member" name="PriceRange4Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestNumber" name="SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestNumber" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="icfi_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestWeightedAverageGrantDateFairValue" name="SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestWeightedAverageGrantDateFairValue" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="icfi_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestAggregateIntrinsicValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestAggregateIntrinsicValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="icfi_NumberOfPerformancePeriodInPerformanceBasedShareProgram" name="NumberOfPerformancePeriodInPerformanceBasedShareProgram" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PercentageOfMultiplicationAwardByProduct" name="PercentageOfMultiplicationAwardByProduct" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodAsAdjusted" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodAsAdjusted" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVest" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVest" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_LineOfCreditFacilityConditionForUnlimitedShareRepurchasesLeverageRatio" name="LineOfCreditFacilityConditionForUnlimitedShareRepurchasesLeverageRatio" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="icfi_DeferredCompensationInvestmentsInCashSurrenderLifeInsuranceMember" name="DeferredCompensationInvestmentsInCashSurrenderLifeInsuranceMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_DeferredCompensationPlanLiabilitiesMember" name="DeferredCompensationPlanLiabilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_ContingentLiabilityRelatedToAcquisitionMember" name="ContingentLiabilityRelatedToAcquisitionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_AccruedExpensesAndOtherCurrentLiabilitiesMember" name="AccruedExpensesAndOtherCurrentLiabilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_ContractTermPeriod" name="ContractTermPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_ContractAwardValue" name="ContractAwardValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_RoadHomeContractMember" name="RoadHomeContractMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_OCDVsICFEmergencyMember" name="OCDVsICFEmergencyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_CommunityDevelopmentRelatedToClaim" name="CommunityDevelopmentRelatedToClaim" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_MaximumDeferOfCompensationSubjectToStatutoryLimitationsPercentage" name="MaximumDeferOfCompensationSubjectToStatutoryLimitationsPercentage" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PercentageOfEmployerMatchingContributionsConditionOne" name="PercentageOfEmployerMatchingContributionsConditionOne" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PercentageOfEmployeeEntitledToEmployerMatchingContributionConditionOne" name="PercentageOfEmployeeEntitledToEmployerMatchingContributionConditionOne" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PercentageOfEmployerMatchingContributionsConditionTwo" name="PercentageOfEmployerMatchingContributionsConditionTwo" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PercentageOfEmployeeEntitledToEmployerMatchingContributionConditionTwo" name="PercentageOfEmployeeEntitledToEmployerMatchingContributionConditionTwo" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_DeferredCompensationOnPerformanceBonusesThatEligibleEmployeePercentage" name="DeferredCompensationOnPerformanceBonusesThatEligibleEmployeePercentage" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_EmployeeStockPurchasePlanSharesAuthorized" name="EmployeeStockPurchasePlanSharesAuthorized" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="icfi_EmployeeStockPurchasePlanAnnualMaximumPayrollDeduction" name="EmployeeStockPurchasePlanAnnualMaximumPayrollDeduction" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_StockIssuedDuringPeriodValueEmployeeStockPurchasePlansPerShare" name="StockIssuedDuringPeriodValueEmployeeStockPurchasePlansPerShare" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_EmployeeStockPurchasePlanNumberOfSharesAvailableForGrant" name="EmployeeStockPurchasePlanNumberOfSharesAvailableForGrant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="icfi_ITGMember" name="ITGMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_PurchasePriceOfEscrowAccountForIndemnificationClaims" name="PurchasePriceOfEscrowAccountForIndemnificationClaims" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="icfi_AllowanceForDoubtfulAccountsForeignCurrencyTranslation" name="AllowanceForDoubtfulAccountsForeignCurrencyTranslation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
</xsd:schema>
