<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-06-21</periodOfReport>

    <notSubjectToSection16>true</notSubjectToSection16>

    <issuer>
        <issuerCik>0001838672</issuerCik>
        <issuerName>AdTheorent Holding Company, Inc.</issuerName>
        <issuerTradingSymbol>ADTH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001900547</rptOwnerCik>
            <rptOwnerName>Lawson James A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ADTHEORENT HOLDING COMPANY, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>330 HUDSON STREET, 13TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10013</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>Chief Executive Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-06-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2481450</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.21</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.47</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2024-06-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>820668</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2027-10-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>820668</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.74</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2024-06-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>945858</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2029-05-06</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>945858</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the Agreement and Plan of Merger, dated as of April 1, 2024 (the &quot;Merger Agreement&quot;), by and among Issuer, Cadent, LLC, a limited liability corporation organized under the laws of Delaware (&quot;Parent&quot;), Award Merger Sub, Inc., a Delaware corporation and wholly-owned subsidiary of Parent, and the other parties listed thereto, each share of Issuer common stock, par value $0.0001 per share, then outstanding (with certain exceptions) was converted into the right to receive $3.21 in cash without interest, subject to applicable withholding taxes. In addition, pursuant to the Merger Agreement, each Issuer restricted stock unit award became fully vested and was automatically cancelled and converted into the right to receive $3.21 in cash without interest, subject to applicable withholding taxes.</footnote>
        <footnote id="F2">This Option grant was vested in full on December 31, 2020.</footnote>
        <footnote id="F3">This Option grant was vested in full on December 31, 2022.</footnote>
        <footnote id="F4">Pursuant to the Merger Agreement, each Issuer stock option award became fully vested and was automatically cancelled and converted into the right to receive, in cash without interest, an amount by which $3.21 exceeds the applicable stock option exercise price, subject to applicable withholding taxes.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Thomas P. Conaghan, Attorney-in-Fact</signatureName>
        <signatureDate>2024-06-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
