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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2013-08-02</periodOfReport>

    <dateOfOriginalSubmission>2013-08-06</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001476493</rptOwnerCik>
            <rptOwnerName>Stewart Robert A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>MORRIS CORPORATE CENTER III</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PARSIPPANY</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07054</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Pres-Global Operations</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.0033</value>
            </securityTitle>
            <transactionDate>
                <value>2013-08-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>14564</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>136.0202</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>73891</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Includes shares of restricted stock issued pursuant to the Fourth Amendment and Restatement of the 2001 Incentive Award Plan of Actavis, Inc., as amended.</footnote>
        <footnote id="F2">This amendment to Form 4 is filed solely to correct the transaction code in Box 3 to reflect a sale rather than a forteiture of shares on the transaction date.</footnote>
        <footnote id="F3">The price reported in Column 4 is a weighted average price.  These shares were sold in multiple transactions at prices ranging from $135.45 to $136.44, inclusive.  The reporting person undertakes to provide to Actaivs, Inc., any security holder of Actavis, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote (3) to this Form 4.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Robert A. Stewart</signatureName>
        <signatureDate>2013-08-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
