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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-01-23</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001010286</issuerCik>
        <issuerName>FiberTower CORP</issuerName>
        <issuerTradingSymbol>FTWRQ</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001407737</rptOwnerCik>
            <rptOwnerName>Solus Alternative Asset Management LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>410 PARK AVENUE, 11TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</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>0001465912</rptOwnerCik>
            <rptOwnerName>Solus GP LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>410 PARK AVENUE, 11TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</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>0001465911</rptOwnerCik>
            <rptOwnerName>Pucillo Christopher</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>410 PARK AVENUE, 11TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</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, par value $0.0001 per share (&quot;Common Stock&quot;)</value>
            </securityTitle>
            <transactionDate>
                <value>2013-01-23</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>367500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>.02</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5635226</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The securities to which this Form 4 relates were held directly by certain funds and accounts (collectively, the &quot;Clients&quot;) managed by Solus Alternative Asset Management LP (&quot;Solus&quot;). This Form 4 shall not be construed as an admission that any Client is the beneficial owner of any shares of Common Stock. Solus, a Delaware limited partnership, is a registered investment adviser that serves as investment adviser to the Clients, and as such has discretion over the securities held by the Clients. Pursuant to Rule 16a-1(a)(1), Solus is not deemed to beneficially own the securities held by the Funds but has elected to file this Form 4 nevertheless.</footnote>
        <footnote id="F2">Solus GP LLC (&quot;Solus GP&quot;) is the general partner of Solus. Solus GP does not beneficially own any such securities as the term &quot;beneficial owner&quot; is defined in Rule 16a-1(a)(2) but has elected to file this Form 4 nevertheless.</footnote>
        <footnote id="F3">Christopher Pucillo is the managing member of Solus GP. Mr. Pucillo disclaims beneficial ownership of the securities held directly by the Clients pursuant to Rule 16a-1(a)(4), except to the extent of his indirect pecuniary interest, if any, in such securities as a result of his interest in affiliates of Solus or the Clients.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Christopher Pucillo, as Managing Member of Solus GP LLC, the General Partner of Solus Alternative Asset Management LP</signatureName>
        <signatureDate>2013-01-25</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Christopher Pucillo, as Managing Member of Solus GP LLC</signatureName>
        <signatureDate>2013-01-25</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Christopher Pucillo</signatureName>
        <signatureDate>2013-01-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
