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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-06-12</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001397911</issuerCik>
        <issuerName>LPL Financial Holdings Inc.</issuerName>
        <issuerTradingSymbol>LPLA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001249554</rptOwnerCik>
            <rptOwnerName>SCHIFTER RICHARD P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TPG GLOBAL, LLC,</rptOwnerStreet1>
            <rptOwnerStreet2>301 COMMERCE STREET, SUITE 3300</rptOwnerStreet2>
            <rptOwnerCity>FORT WORTH</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>76102</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.001 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2013-06-12</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6246</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14343</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The shares of Common Stock (each, a &quot;Share&quot;) of LPL Financial Holdings Inc. (the &quot;Issuer&quot;) reported herein were received in a pro rata distribution of Shares from each of TPG Equity IV-A, L.P. and TPG GenPar IV, L.P.  Of the Shares reported herein, 1,511 Shares were received from Equity IV-A and 4,735 Shares were received from GenPar IV.</footnote>
        <footnote id="F2">Mr. Schifter is a TPG partner.  TPG is affiliated with each of TPG Holdings I, L.P. (&quot;Holdings I&quot;), which holds 424,827 Shares (the &quot;Holdings I Shares&quot;), and TPG Partners IV, L.P. (&quot;Partners IV&quot;), which holds 20,710,185 Shares (the &quot;Partners IV Shares&quot; and, together with the Holdings I Shares, the &quot;TPG Shares&quot;).</footnote>
        <footnote id="F3">Mr. Schifter disclaims beneficial ownership of the TPG Shares and any Shares that are or may be beneficially owned by any affiliate of Holdings I or Partners IV. Pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, as amended (the &quot;Exchange Act&quot;), this filing shall not be deemed an admission that Mr. Schifter is, for purposes of Section 16 of the Exchange Act or otherwise, the beneficial owner of any equity securities of the Issuer directly held by Holdings I, Partners IV or any of their respective affiliates.</footnote>
    </footnotes>

    <remarks>(4) Ronald Cami is signing on behalf of Mr. Schifter pursuant to an authorization and designation letter dated July 1, 2010, which is filed as an exhibit to this Form 4.</remarks>

    <ownerSignature>
        <signatureName>/s/ Ronald Cami on behalf of Richard P. Schifter (4)</signatureName>
        <signatureDate>2013-06-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
