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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-02-28</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000826773</issuerCik>
        <issuerName>UniTek Global Services, Inc.</issuerName>
        <issuerTradingSymbol>UNTK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001400314</rptOwnerCik>
            <rptOwnerName>SECTOR PERFORMANCE FUND LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O HM CAPITAL PARTNERS LLC</rptOwnerStreet1>
            <rptOwnerStreet2>200 CRESCENT COURT, SUITE 1600</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001483604</rptOwnerCik>
            <rptOwnerName>HM UNITEK COINVEST, LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O HM CAPITAL PARTNERS LLC</rptOwnerStreet1>
            <rptOwnerStreet2>200 CRESCENT COURT, SUITE 1600</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001483596</rptOwnerCik>
            <rptOwnerName>SPF SBS LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O HM CAPITAL PARTNERS LLC</rptOwnerStreet1>
            <rptOwnerStreet2>200 CRESCENT COURT, SUITE 1600</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001483597</rptOwnerCik>
            <rptOwnerName>SECTOR PERFORMANCE GP, LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O HM CAPITAL PARTNERS LLC</rptOwnerStreet1>
            <rptOwnerStreet2>200 CRESCENT COURT, SUITE 1600</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001483598</rptOwnerCik>
            <rptOwnerName>SECTOR PERFORMANCE LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O HM CAPITAL PARTNERS LLC</rptOwnerStreet1>
            <rptOwnerStreet2>200 CRESCENT COURT, SUITE 1600</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-02-28</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>178888</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-02-28</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4342376</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.30</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Sector Performance Fund, LP (&quot;Sector Performance Fund&quot;) was the direct beneficial owner of 4,028,839 shares of Common Stock.  SPF SBS LP (&quot;SPF SBS&quot;) was the direct beneficial owner of 254,574 shares of Common Stock.   HM Unitek Coinvest, LP (&quot;Coinvest&quot;) was the direct beneficial owner of 237,851shares of Common Stock.  Each of Sector Performance GP, Coinvest and SPF SBS entered into a series of related transactions with UniTek Interposed LP (&quot;UniTek Interposed&quot;) and certain other parties thereto, pursuant to which, among other transactions, each of them transferred to UniTek Interposed all of their respective shares of Common Stock in exchange for, through a series of transactions, either (i) an allocable portion of non-voting limited partner interests in UniTek Interposed or (ii) cash equal to $4.30 per share of Common Stock.</footnote>
        <footnote id="F2">Sector Performance GP, LP (&quot;Sector Performance GP&quot;) is the general partner of Sector Performance Fund and, as a result thereof, Sector Performance GP may be deemed to share beneficial ownership with respect to the securities directly owned by Sector Performance GP.  Sector Performance LLC (&quot;Ultimate GP&quot;) is the general partner of Sector Performance GP, Coinvest and SPF SBS and, as a result thereof, Ultimate GP may be deemed to share beneficial ownership with respect to the securities directly owned by Sector Performance GP, Coinvest and SPF SBS.  Except for direct holdings and to the extent of any pecuniary interests, each of Sector Performance GP and Ultimate GP expressly disclaims the existence of such beneficial ownership.</footnote>
    </footnotes>

    <remarks>See Exhibit 99.1 - Signature and Exhibit 99.2 - Joint Filer Information.</remarks>

    <ownerSignature>
        <signatureName>See Exhibit 99.1</signatureName>
        <signatureDate>2013-02-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
