-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 H1Bk1aOz8lnVrbgZ3aWbWJmUbFUKLCg+1CpHE9cVsZHN2t43nirxQlJxUQ31ePKe
 G+duSasIib41irAXNBFOIw==

<SEC-DOCUMENT>0001438471-10-000001.txt : 20100812
<SEC-HEADER>0001438471-10-000001.hdr.sgml : 20100812
<ACCEPTANCE-DATETIME>20100812190020
ACCESSION NUMBER:		0001438471-10-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100811
FILED AS OF DATE:		20100812
DATE AS OF CHANGE:		20100812

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Brady Laura
		CENTRAL INDEX KEY:			0001438471

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24033
		FILM NUMBER:		101012585

	MAIL ADDRESS:	
		STREET 1:		4949 WORNALL ROAD #300
		CITY:			KANSAS CITY
		STATE:			MO
		ZIP:			64112

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>2010-08-11</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001438471</rptOwnerCik>
            <rptOwnerName>Brady Laura</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>4949 WORNALL ROAD #300</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>KANSAS CITY</rptOwnerCity>
            <rptOwnerState>MO</rptOwnerState>
            <rptOwnerZipCode>64112</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 ($0.15 par value)</value>
            </securityTitle>
            <transactionDate>
                <value>2010-08-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.36</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>Laura Brady</signatureName>
        <signatureDate>2010-08-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----