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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-06-18</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001365038</issuerCik>
        <issuerName>LEAF GROUP LTD.</issuerName>
        <issuerTradingSymbol>LEAF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001778484</rptOwnerCik>
            <rptOwnerName>Gephart Brian</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1655 26TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SANTA MONICA</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90404</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>See Remarks</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $.0001 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2020-06-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>30000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>60000</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">In connection with Mr. Gephart's appointment as the interim Chief Financial Officer of Leaf Group Ltd. (the &quot;Company&quot;) in May 2020, Mr. Gephart was granted 30,000 restricted stock units (&quot;RSUs&quot;). Each RSU represents the right to receive one share of the Company's common stock upon vesting. Subject to Mr. Gephart's continued employment through the applicable vesting date, 10,000 RSUs shall vest on April 1, 2021, and the remaining 20,000 RSUs shall vest in 24 substantially equal installments on each monthly anniversary thereafter.</footnote>
        <footnote id="F2">Includes 60,000 unvested RSUs.</footnote>
    </footnotes>

    <remarks>Title: Chief Accounting Officer and Interim Chief Financial Officer</remarks>

    <ownerSignature>
        <signatureName>/s/ Adam Wergeles, as attorney-in-fact for Brian Gephart</signatureName>
        <signatureDate>2020-06-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
