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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-09-03</periodOfReport>

    <issuer>
        <issuerCik>0001748824</issuerCik>
        <issuerName>Acadian Asset Management Inc.</issuerName>
        <issuerTradingSymbol>AAMI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001035674</rptOwnerCik>
            <rptOwnerName>PAULSON &amp; CO. INC.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>15 EXCHANGE PLACE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>JERSEY CITY</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07302</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isTenPercentOwner>true</isTenPercentOwner>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.001</value>
            </securityTitle>
            <transactionDate>
                <value>2025-09-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1206839</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>47.69</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7743282</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Managed Funds</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Paulson &amp; Co. Inc. (&quot;Paulson&quot;) is the investment manager of investment funds (the &quot;Funds&quot;). John Paulson is the controlling person of Paulson. All securities reported on this Form 4 are owned by the Funds.</footnote>
        <footnote id="F2">Each of Paulson and John Paulson may be deemed to indirectly beneficially own the securities directly owned by the Funds. Pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, as amended (the &quot;Act&quot;), the filing of this Form 4 shall not be deemed an admission by any person reporting on this Form 4 that such person, for purposes of Section 16 of the Act or otherwise, is the beneficial owner of any equity securities covered by this Form 4.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Stuart L. Merzer, Stuart L. Merzer, General Counsel &amp; Chief Compliance Officer</signatureName>
        <signatureDate>2025-09-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
