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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-07-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001001902</issuerCik>
        <issuerName>INTEVAC INC</issuerName>
        <issuerTradingSymbol>IVAC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001458693</rptOwnerCik>
            <rptOwnerName>Drapkin Matthew A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>500 CRESCENT COURT</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 230</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</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</value>
            </securityTitle>
            <transactionDate>
                <value>2014-07-09</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>50000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.000</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1251620</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-07-10</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>32358</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.000</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1283978</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents common stock (&quot;Common Stock&quot;), par value $0.001 per share, of Intevac, Inc. (the &quot;Issuer&quot;) purchased pursuant to a 10b5-1 plan.</footnote>
        <footnote id="F2">Represents Common Stock directly beneficially owned by Becker Drapkin Partners (QP), L.P. (&quot;Becker Drapkin QP&quot;) (940,025 shares), Becker Drapkin Partners, L.P. (&quot;Becker Drapkin, L.P.&quot;) (175,644 shares) and Common Stock directly held by a managed account on behalf of an investment advisory client (the &quot;Managed Account&quot;) of Becker Drapkin Management, L.P. (&quot;BD Management&quot;) (168,309 shares).  (continued in Footnote 3).</footnote>
        <footnote id="F3">Mr. Drapkin may be deemed to beneficially own such Common Stock as he is a co-managing member of BC Advisors, LLC, which is the general partner of BD Management (of which Mr. Drapkin is a limited partner), and BD Management is the general partner of, and investment manager for, each of Becker Drapkin QP and Becker Drapkin, L.P, and the investment manager of the Managed Account.  Mr. Drapkin disclaims beneficial ownership in such Common Stock except to the extent of his pecuniary interest therein.</footnote>
    </footnotes>

    <remarks>Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

*     If the form is filed by more than one reporting person, see Instruction 4(b)(v).

**    Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note:  File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.

Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.</remarks>

    <ownerSignature>
        <signatureName>/s/ Andrew S. McLelland, attorney-in-fact</signatureName>
        <signatureDate>2014-07-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
