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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-09-30</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000884629</issuerCik>
        <issuerName>Actavis, Inc.</issuerName>
        <issuerTradingSymbol>ACT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001237253</rptOwnerCik>
            <rptOwnerName>BISARO PAUL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>MORRIS CORPORATE CENTER III</rptOwnerStreet1>
            <rptOwnerStreet2>400 INTERPACE PARKWAY</rptOwnerStreet2>
            <rptOwnerCity>PARSIPPANY</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07054</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President &amp; CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.0033</value>
            </securityTitle>
            <transactionDate>
                <value>2013-09-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>140760</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>602992</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.0033</value>
            </securityTitle>
            <transactionDate>
                <value>2013-09-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>162076</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>144.00</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>440916</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.0033</value>
            </securityTitle>
            <transactionDate>
                <value>2013-10-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>440916</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On October  1, 2013, Actavis, Inc. (&quot;Actavis&quot;), Warner Chilcott Public Limited Company (&quot;Warner Chilcott&quot;) and a newly formed holding company incorporated in Ireland named Actavis plc (&quot;New Actavis&quot;) consummated a transaction (the &quot;Acquisition&quot;) pursuant to which Actavis and Warner Chilcott each became wholly owned subsidiaries of New Actavis. The Acquisition was effected by means of an approved &quot;scheme arrangement&quot; under Irish law.</footnote>
        <footnote id="F2">Represents shares of Actavis earned pursuant to outstanding performance-based restricted stock units, based on shortened performance periods resulting from the Acquisition.</footnote>
        <footnote id="F3">Represents shares of Actavis withheld in payment of tax withholding obligations from the accelerated vesting of restricted shares, and the issuance of shares pursuant to performance based restricted stock units.</footnote>
        <footnote id="F4">Represents shares of Actavis disposed of pursuant to the Acquisition in exchange for ordinary shares of New Actavis. At the effective time of the Acquisition, each Actavis common share and accelerated restricted share was converted into the right to receive one New Actavis ordinary share.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ David A. Buchen, Attorney-in-Fact for the Reporting Person</signatureName>
        <signatureDate>2013-10-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
