<?xml version="1.0" encoding="us-ascii"?>
<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2022-08-03T19:39:45.6368563+00:00 -->
<!-- Version            : 5.0.1.747 -->
<!-- Package ID         : bd8352ae86f349f4a2a4b0926461bcba -->
<!-- Copyright (c) 2022 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="icfi_SafetyAndSecurityMember" name="SafetyAndSecurityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_ConsumerAndFinancialMember" name="ConsumerAndFinancialMember" 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_USStateAndLocalGovernmentMember" name="USStateAndLocalGovernmentMember" 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_USStateAndInternationalGovernmentMember" name="USStateAndInternationalGovernmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <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_CostBasedContractMember" name="CostBasedContractMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_ContractWithCustomerAssetsLiabilitiesNetCurrent" name="ContractWithCustomerAssetsLiabilitiesNetCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <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_ChangeInContractWithCustomerAssetNetCurrent" name="ChangeInContractWithCustomerAssetNetCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <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_PercentageOfChangeInContractWithCustomerAssetNetCurrent" name="PercentageOfChangeInContractWithCustomerAssetNetCurrent" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PercentageOfChangeInContractWithCustomerLiabilityCurrent" name="PercentageOfChangeInContractWithCustomerLiabilityCurrent" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PercentageOfChangeInContractWithCustomerAssetsLiabilitiesNetCurrent" name="PercentageOfChangeInContractWithCustomerAssetsLiabilitiesNetCurrent" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <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="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <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="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_COVID19PandemicMember" name="COVID19PandemicMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_GovernmentAssistanceAxis" name="GovernmentAssistanceAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_GovernmentAssistanceMember" name="GovernmentAssistanceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_CoronavirusAidReliefAndEconomicSecurityActMember" name="CoronavirusAidReliefAndEconomicSecurityActMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_ExercisedOptionToDeferEmployerPortionOfSocialSecurityTaxDescription" name="ExercisedOptionToDeferEmployerPortionOfSocialSecurityTaxDescription" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PercentageOfDeferredEmployerPortionOfSocialSecurityTaxRepayable" name="PercentageOfDeferredEmployerPortionOfSocialSecurityTaxRepayable" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_EmployerPortionOfSocialSecurityTaxRepayableDate" name="EmployerPortionOfSocialSecurityTaxRepayableDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_EmployerPortionOfSocialSecurityTaxRepayableRemainderDate" name="EmployerPortionOfSocialSecurityTaxRepayableRemainderDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_EmployerPortionOfSocialSecurityTaxDeferred" name="EmployerPortionOfSocialSecurityTaxDeferred" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <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_PaymentsForBuyBacksShares" name="PaymentsForBuyBacksShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_PaymentsForBuyBacksSharesValue" name="PaymentsForBuyBacksSharesValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <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_CashSettledRSUsMember" name="CashSettledRSUsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapital" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapital" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="icfi_CreativeSystemsMember" name="CreativeSystemsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_ITGMember" name="ITGMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_IndemnityMember" name="IndemnityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_BusinessAcquisitionDiscountPercentageOnIndemnityLiabilities" name="BusinessAcquisitionDiscountPercentageOnIndemnityLiabilities" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="icfi_BusinessCombinationNumberOfPaymentOutstanding" name="BusinessCombinationNumberOfPaymentOutstanding" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" 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_LineOfCreditFacilityConditionForUnlimitedShareRepurchasesLeverageRatio" name="LineOfCreditFacilityConditionForUnlimitedShareRepurchasesLeverageRatio" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="icfi_NetLiquidityAmount" name="NetLiquidityAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="icfi_ShareRepurchaseApprovedStartingOnDecemberTwentyTwentyTwentyOneAndEndingNoLaterThanJuneThirtyTwentyTwentyTwoMember" name="ShareRepurchaseApprovedStartingOnDecemberTwentyTwentyTwentyOneAndEndingNoLaterThanJuneThirtyTwentyTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_CreditFacilityMember" name="CreditFacilityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_DeferredCompensationInvestmentsInCashSurrenderLifeInsuranceMember" name="DeferredCompensationInvestmentsInCashSurrenderLifeInsuranceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <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_AccruedExpensesAndOtherCurrentLiabilitiesMember" name="AccruedExpensesAndOtherCurrentLiabilitiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_SemanticBitsLLCMember" name="SemanticBitsLLCMember" type="dtr-types: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="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="icfi_OCDVsICFEmergencyMember" name="OCDVsICFEmergencyMember" type="dtr-types: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_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedAcceleratedAndVestedNumber" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedAcceleratedAndVestedNumber" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
</xsd:schema>
