<SEC-DOCUMENT>0001842718-25-000004.txt : 20250107
<SEC-HEADER>0001842718-25-000004.hdr.sgml : 20250107
<ACCEPTANCE-DATETIME>20250107175940
ACCESSION NUMBER:		0001842718-25-000004
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250103
FILED AS OF DATE:		20250107
DATE AS OF CHANGE:		20250107

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			PUTMAN JILL
		CENTRAL INDEX KEY:			0001806834
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-40557
		FILM NUMBER:		25516020

	MAIL ADDRESS:	
		STREET 1:		100 WASHINGTON AVENUE S., SUITE 100
		CITY:			MINNEAPOLIS
		STATE:			MN
		ZIP:			55401

	FORMER NAME:	
		FORMER CONFORMED NAME:	PUTNAM JILL
		DATE OF NAME CHANGE:	20200316

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			INTEGRAL AD SCIENCE HOLDING CORP.
		CENTRAL INDEX KEY:			0001842718
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER PROGRAMMING, DATA PROCESSING, ETC. [7370]
		ORGANIZATION NAME:           	06 Technology
		IRS NUMBER:				830731995
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		99 WALL STREET
		STREET 2:		#1950
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10005
		BUSINESS PHONE:		(646) 278-4871

	MAIL ADDRESS:	
		STREET 1:		99 WALL STREET
		STREET 2:		#1950
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10005

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	INTEGRAL AD SCIENCE HOLDING LLC
		DATE OF NAME CHANGE:	20210301

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	KAVACHA TOPCO, LLC
		DATE OF NAME CHANGE:	20210127
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wk-form4_1736290774.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-01-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001842718</issuerCik>
        <issuerName>INTEGRAL AD SCIENCE HOLDING CORP.</issuerName>
        <issuerTradingSymbol>IAS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001806834</rptOwnerCik>
            <rptOwnerName>PUTMAN JILL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O INTEGRAL AD SCIENCE HOLDING CORP.</rptOwnerStreet1>
            <rptOwnerStreet2>12 E. 49TH STREET, 20TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10017</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Interim CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $0.001 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2025-01-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>108968</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>157095</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents Restricted Stock Units which will be settled in shares of common stock of the Issuer and will vest over a 1 year period with 16.67% vesting each month for the first three months and the remaining amount in 9 equal installments of 5.56%, in each case, subject to the Reporting Persons continued service as Interim Chief Financial Officer of the Issuer.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Yossi Almani, by Power of Attorney</signatureName>
        <signatureDate>2025-01-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
