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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-01-24</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001374993</issuerCik>
        <issuerName>NextWave Wireless Inc.</issuerName>
        <issuerTradingSymbol>WAVE.PK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001367608</rptOwnerCik>
            <rptOwnerName>Cassou Frank A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O NEXTWAVE WIRELESS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>12264 EL CAMINO REAL, SUITE 305</rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92130</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP &amp; Chief Legal Counsel</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-01-24</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>348506</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>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-01-24</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>750000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">NextWave Wireless Inc. (the &quot;Issuer&quot;) was acquired (the &quot;Merger&quot;) pursuant to that certain Agreement and Plan of Merger, dated as of August 1, 2012 (the &quot;Merger Agreement&quot;), by and among the Issuer, AT&amp;T Inc. (&quot;Parent&quot;), and Rodeo Acquisition Sub Inc., a wholly owned subsidiary of Parent (&quot;Merger Sub&quot;). All shares of the Issuer's common stock, par value $0.007 per share (&quot;Common Stock&quot;), held by the Reporting Person at the effective time of the Merger (the &quot;Effective Time&quot;) were exchanged for merger consideration consisting of (i) $1.00 in cash per share of Common Stock, and (ii) one contingent payment right, representing a pro rata interest in an amount up to $25 million in an escrow account, which will be subject to reduction (including, to $0) in the event that indemnification claims or other amounts become payable to Parent, as described in the Merger Agreement.</footnote>
        <footnote id="F2">Represents shares of Common Stock received as a restricted stock award by the Reporting Person that were exchanged for merger consideration in the Merger.  All stock options held by the Reporting Person were cancelled as of the Effective Time for no value.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Frank Cassou</signatureName>
        <signatureDate>2013-01-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
