<SUBMISSION>
<ACCESSION-NUMBER>0001069258-08-000008
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20080104
<FILING-DATE>20080708
<DATE-OF-FILING-DATE-CHANGE>20080708
<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>1228
</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>Liberatore Samuel N
<CIK>0001435919
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-27231
<FILM-NUMBER>08942655
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>256-864-7200
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>401 WYNN DRIVE
<CITY>HUNTSVILLE
<STATE>AL
<ZIP>35805
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</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>0001435919</rptOwnerCik>
            <rptOwnerName>Liberatore Samuel N</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>401 WYNN DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HUNTSVILLE</rptOwnerCity>
            <rptOwnerState>AL</rptOwnerState>
            <rptOwnerZipCode>35805</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Pres. Madison Research Div.</otherText>
        </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>20000</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>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>52500</value>
                    <footnoteId id="F3"/>
                </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 five 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>
        <footnote id="F3">Includes 12,500 Restricted Stock Units and 20,000 Employee Stock Options previously reported on Form 3 filed on July 8, 2008.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Samuel N. Liberatore, by Matthew G. Colvin, Attorney-In-Fact</signatureName>
        <signatureDate>2008-07-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
