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

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    <periodOfReport>2013-11-22</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000110536</issuerCik>
        <issuerName>NATIONAL TECHNICAL SYSTEMS INC /CA/</issuerName>
        <issuerTradingSymbol>NTSC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001199700</rptOwnerCik>
            <rptOwnerName>MCGINNIS WILLIAM</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>24007 VENTURA BLVD</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>CALABASAS</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91302</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CHIEF EXECUTIVE OFFICER</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

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                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionAmounts>
                <transactionShares>
                    <value>126087</value>
                </transactionShares>
                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
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                <sharesOwnedFollowingTransaction>
                    <value>13480</value>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By wife</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
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    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
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            <transactionDate>
                <value>2013-11-22</value>
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                    <value>D</value>
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            <expirationDate>
                <value>2014-06-28</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
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                <underlyingSecurityShares>
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            </underlyingSecurity>
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                <value>2013-11-22</value>
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                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                <transactionPricePerShare>
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                <underlyingSecurityTitle>
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                <underlyingSecurityShares>
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            </underlyingSecurity>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Appreciation Rights</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>7.50</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2013-11-22</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionAmounts>
                <transactionShares>
                    <value>250000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-12-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>250000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
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        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Disposed of pursuant to a contribution agreement dated November 21, 2013 between the reporting person and NTS Holding Corporation, Inc. (&quot;NTS Holding&quot;), the sole owner of Nest Parent, Inc., in exchange for newly issued shares of NTS Holding, valuing the contributed securities at $23.00 per share.</footnote>
        <footnote id="F2">Disposed of pursuant to the Agreement and Plan of Merger, dated as of August 15, 2013, between National Technical Systems, Inc. (the &quot;Company&quot;), Nest Parent, Inc. and Nest Merger Sub, Inc. (the &quot;Merger Agreement&quot;) in exchange for a cash payment of $23.00 per share.</footnote>
        <footnote id="F3">Pursuant to the Merger Agreement, each outstanding stock option, whether vested or unvested, was canceled and converted into the right to receive a cash payment representing the amount, if any, by which $23.00 exceeded the exercise price per share of common stock underlying such stock option.</footnote>
        <footnote id="F4">In connection with the consummation of the transactions contemplated by the Merger Agreement, each vested phantom stock appreciation right was canceled and converted into the right to receive a cash payment representing the amount, if any, by which $23.00 exceeded the applicable grant price per phantom stock appreciation right.  On October 23, 2012, the compensation committee of the Company's board of directors exercised its discretion to accelerate the vesting of all phantom stock appreciation rights in connection with a change of control occurring before October 23, 2014.  Accordingly, all outstanding and unvested phantom stock appreciation rights vested upon the consummation of the transactions contemplated by the Merger Agreement and were cancelled in exchange for the aforementioned consideration.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ William McGinnis</signatureName>
        <signatureDate>2013-11-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
