-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 Jq6C2nhu2Dq2FmhDMrQexG1vj0mmTEhHUWTsjX+kxxwtR/w9euXjfej9KG59EG5V
 Hbrp8JsNjJ0U8mHfcRKTsQ==

<SEC-DOCUMENT>0001258977-10-000002.txt : 20100830
<SEC-HEADER>0001258977-10-000002.hdr.sgml : 20100830
<ACCEPTANCE-DATETIME>20100830190354
ACCESSION NUMBER:		0001258977-10-000002
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100830
FILED AS OF DATE:		20100830
DATE AS OF CHANGE:		20100830

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HANCOCK LINDA S
		CENTRAL INDEX KEY:			0001258977

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24033
		FILM NUMBER:		101047994

	MAIL ADDRESS:	
		STREET 1:		1025 W 58TH STREET
		CITY:			KANSAS CITY
		STATE:			MO
		ZIP:			64113

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NASB FINANCIAL INC
		CENTRAL INDEX KEY:			0001059131
		STANDARD INDUSTRIAL CLASSIFICATION:	SAVINGS INSTITUTION, FEDERALLY CHARTERED [6035]
		IRS NUMBER:				431805201
		STATE OF INCORPORATION:			MO
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		12498 SOUTH 71 HIGHWAY
		CITY:			GRANDVIEW
		STATE:			MO
		ZIP:			64030
		BUSINESS PHONE:		8167652200

	MAIL ADDRESS:	
		STREET 1:		12498 SOUTH 71 HIGHWAY
		CITY:			GRANDVIEW
		STATE:			MO
		ZIP:			64030
</SEC-HEADER>
<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>2010-08-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001059131</issuerCik>
        <issuerName>NASB FINANCIAL INC</issuerName>
        <issuerTradingSymbol>NASB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001258977</rptOwnerCik>
            <rptOwnerName>HANCOCK LINDA S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1025 W 58TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>KANSAS CITY</rptOwnerCity>
            <rptOwnerState>MO</rptOwnerState>
            <rptOwnerZipCode>64113</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock ($0.15 par value)</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>264068</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common stock ($0.15 par value)</value>
            </securityTitle>
            <transactionDate>
                <value>2010-08-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6377</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.64</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3948580</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The reporting person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that the person reporting is the beneficial owner of such securities for the purpose of Section 16 or for any other purposes.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Linda S. Hancock</signatureName>
        <signatureDate>2010-08-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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