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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 ncXBYCre0+A5uEeJsgWv+A==

<SEC-DOCUMENT>0001025692-10-000006.txt : 20101214
<SEC-HEADER>0001025692-10-000006.hdr.sgml : 20101214
<ACCEPTANCE-DATETIME>20101214162728
ACCESSION NUMBER:		0001025692-10-000006
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20101214
FILED AS OF DATE:		20101214
DATE AS OF CHANGE:		20101214

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

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HANCOCK DAVID H
		CENTRAL INDEX KEY:			0001025692

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24033
		FILM NUMBER:		101250879

	MAIL ADDRESS:	
		STREET 1:		12498 S 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>2010-12-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001025692</rptOwnerCik>
            <rptOwnerName>HANCOCK DAVID H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>12498 S 71 HIGHWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>GRANDVIEW</rptOwnerCity>
            <rptOwnerState>MO</rptOwnerState>
            <rptOwnerZipCode>64030</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common stock ($0.15 par value)</value>
            </securityTitle>
            <transactionDate>
                <value>2010-12-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>16.49</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3881692</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock ($0.15 par value)</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>264068</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>David H. Hancock</signatureName>
        <signatureDate>2010-12-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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