<SEC-DOCUMENT>0000939057-19-000412.txt : 20191113
<SEC-HEADER>0000939057-19-000412.hdr.sgml : 20191113
<ACCEPTANCE-DATETIME>20191113103709
ACCESSION NUMBER:		0000939057-19-000412
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20191101
FILED AS OF DATE:		20191113
DATE AS OF CHANGE:		20191113

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			FULLER ROBERT B
		CENTRAL INDEX KEY:			0001368780

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-35589
		FILM NUMBER:		191212220

	MAIL ADDRESS:	
		STREET 1:		111 NORTH WALL STREET
		CITY:			SPOKANE
		STATE:			WA
		ZIP:			99201

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FS Bancorp, Inc.
		CENTRAL INDEX KEY:			0001530249
		STANDARD INDUSTRIAL CLASSIFICATION:	SAVINGS INSTITUTIONS, NOT FEDERALLY CHARTERED [6036]
		IRS NUMBER:				454585178
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		6920 220TH STREET SW
		STREET 2:		SUITE 300
		CITY:			MOUNTLAKE TERRACE
		STATE:			WA
		ZIP:			98043
		BUSINESS PHONE:		800-683-0973

	MAIL ADDRESS:	
		STREET 1:		6920 220TH STREET SW
		STREET 2:		SUITE 300
		CITY:			MOUNTLAKE TERRACE
		STATE:			WA
		ZIP:			98043
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-11-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001530249</issuerCik>
        <issuerName>FS Bancorp, Inc.</issuerName>
        <issuerTradingSymbol>FSBW</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001368780</rptOwnerCik>
            <rptOwnerName>FULLER ROBERT B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>6920 220TH STREET SW</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MOUNTLAKE TERRACE</rptOwnerCity>
            <rptOwnerState>WA</rptOwnerState>
            <rptOwnerZipCode>98043</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Credit Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-11-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>57.14</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>11660</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-11-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>240</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>58.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>11420</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The reported price in Column 4 is a weighted average price.  These shares were sold in multiple transactions at prices ranging from $57.00 to $57.25 per share, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote (1).</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/Robert B. Fuller</signatureName>
        <signatureDate>2019-11-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
