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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-01-20</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001187520</issuerCik>
        <issuerName>DENALI FUND INC.</issuerName>
        <issuerTradingSymbol>DNY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001247992</rptOwnerCik>
            <rptOwnerName>LOLA BROWN TRUST 1B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1029 WEST 3RD AVENUE, SUITE 400</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ANCHORAGE</rptOwnerCity>
            <rptOwnerState>AK</rptOwnerState>
            <rptOwnerZipCode>99503</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001246903</rptOwnerCik>
            <rptOwnerName>HOREJSI STEWART R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 SOUTH SANTA FE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SALINA</rptOwnerCity>
            <rptOwnerState>KS</rptOwnerState>
            <rptOwnerZipCode>67401</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001245558</rptOwnerCik>
            <rptOwnerName>CICIORA SUSAN L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2344 SPRUCE STREET, STE A</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOULDER</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80302</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-01-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1546</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.32</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3132232</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The trustees of the Lola Brown Trust No. 1B (the &quot;Brown Trust&quot;) are Alaska Trust Company (&quot;Alaska Trust&quot;), Susan L. Ciciora and Larry Dunlap.  Such trustees may be deemed to control the Brown Trust and may be deemed to possess indirect beneficial ownership of the Shares held by the Brown Trust.  However, none of the trustees, acting alone, can vote or exercise dispositive authority over Shares held by the Brown Trust.  Accordingly, Alaska Trust, Ms. Ciciora and Mr. Dunlap disclaim beneficial ownership of the Shares beneficially owned, directly or indirectly, by the Brown Trust.  In addition to serving as a trustee, Ms. Ciciora is also a beneficiary of the Brown Trust.

As a result of his advisory role with the Brown Trust, Stewart R. Horejsi may be deemed to have indirect beneficial ownership of the Shares directly beneficially owned by the Brown Trust.  However, Mr. Horejsi disclaims such beneficial ownership of the Shares directly beneficially held by the Brown Trust.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Douglas J. Blattmachr, President, Alaska Trust Company, trustee of the Lola Brown Trust 1B</signatureName>
        <signatureDate>2010-01-21</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Stewart R. Horejsi</signatureName>
        <signatureDate>2010-01-21</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Susan L. Ciciora</signatureName>
        <signatureDate>2010-01-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
