<SEC-DOCUMENT>0001842718-25-000025.txt : 20250306
<SEC-HEADER>0001842718-25-000025.hdr.sgml : 20250306
<ACCEPTANCE-DATETIME>20250306161725
ACCESSION NUMBER:		0001842718-25-000025
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250304
FILED AS OF DATE:		20250306
DATE AS OF CHANGE:		20250306

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Gil Alexis II
		CENTRAL INDEX KEY:			0002001306
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-40557
		FILM NUMBER:		25715488

	MAIL ADDRESS:	
		STREET 1:		95 MORTON STREET
		STREET 2:		8TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10014

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_1741295838.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-03-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002001306</rptOwnerCik>
            <rptOwnerName>Gil Alexis II</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>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Accounting Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $0.001 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2025-03-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3284</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.41</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>119125</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Mandatory sale to cover tax liability associated with the settlement of restricted stock units.</footnote>
        <footnote id="F2">The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $10.28 to $10.56 per share. The reporting person undertakes to provide to Integral Ad Science Holding Corp., any security holder of Integral Ad Science Holding Corp. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth herein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Yossi Almani, by Power of Attorney</signatureName>
        <signatureDate>2025-03-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
