<SUBMISSION>
<ACCESSION-NUMBER>0001114923-08-000001
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20080104
<FILING-DATE>20080107
<DATE-OF-FILING-DATE-CHANGE>20080107
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>KRATOS DEFENSE & SECURITY SOLUTIONS, INC.
<CIK>0001069258
<ASSIGNED-SIC>4899
<IRS-NUMBER>133818604
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>4810 EASTGATE MALL
<STREET2>.
<CITY>SAN DIEGO
<STATE>CA
<ZIP>92121
<PHONE>858-812-7300
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>4810 EASTGATE MALL
<STREET2>.
<CITY>SAN DIEGO
<STATE>CA
<ZIP>92121
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>WIRELESS FACILITIES INC
<DATE-CHANGED>19990817
</FORMER-COMPANY>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>HOGLUND WILLIAM A
<CIK>0001114923
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-27231
<FILM-NUMBER>08514565
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>858-228-2734
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>4810 EASTGATE MALL
<CITY>SAN DIEGO
<STATE>CA
<ZIP>92121
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-01-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001069258</issuerCik>
        <issuerName>KRATOS DEFENSE &amp; SECURITY SOLUTIONS, INC.</issuerName>
        <issuerTradingSymbol>KTOS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001114923</rptOwnerCik>
            <rptOwnerName>HOGLUND WILLIAM A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KRATOS DEFENSE &amp; SECURITY SOLUTIONS</rptOwnerStreet1>
            <rptOwnerStreet2>4810 EASTGATE MALL</rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92121</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-01-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2018-01-04</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each restricted stock unit represents a contingent right to receive one share of issuer's common stock.</footnote>
        <footnote id="F2">The restricted stock units vest in four equal installments beginning January 4, 2009. Vested shares will be delivered to the reporting person on the first date which is administratively practicable for the distribution of the vested shares after termination of service with the issuer.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Matthew G. Colvin, Attorney-In-Fact for William A. Hoglund</signatureName>
        <signatureDate>2008-01-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
