<SEC-DOCUMENT>0001179110-16-031073.txt : 20161102
<SEC-HEADER>0001179110-16-031073.hdr.sgml : 20161102
<ACCEPTANCE-DATETIME>20161102113726
ACCESSION NUMBER:		0001179110-16-031073
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20160929
FILED AS OF DATE:		20161102
DATE AS OF CHANGE:		20161102

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			OLD SECOND BANCORP INC
		CENTRAL INDEX KEY:			0000357173
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				363143493
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1215

	BUSINESS ADDRESS:	
		STREET 1:		37 S RIVER ST
		CITY:			AURORA
		STATE:			IL
		ZIP:			60507
		BUSINESS PHONE:		7088920202

	MAIL ADDRESS:	
		STREET 1:		37 SOUTH RIVER STREET
		CITY:			AURORA
		STATE:			IL
		ZIP:			60507

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Pilmer Donald
		CENTRAL INDEX KEY:			0001673321

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-10537
		FILM NUMBER:		161966759

	MAIL ADDRESS:	
		STREET 1:		37 S. RIVER ST.
		CITY:			AURORA
		STATE:			IL
		ZIP:			60506
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4/A -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2016-09-29</periodOfReport>

    <dateOfOriginalSubmission>2016-11-01</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000357173</issuerCik>
        <issuerName>OLD SECOND BANCORP INC</issuerName>
        <issuerTradingSymbol>OSBC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001673321</rptOwnerCik>
            <rptOwnerName>Pilmer Donald</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>37 S. RIVER ST.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>AURORA</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60506</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Old Second Bancorp, Inc.Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-09-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>34085.054</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Old Second Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-11-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>895</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.015</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>923</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Profit Sharing Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Old Second Bancorp, Inc.Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-11-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>961</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.015</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1026</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>401(k) plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Of this total, 26,500 are restricted stock units, 36.054 shares are dividend equivalents in the form of restricted stock units, 7,539 shares held jointly with spouse in a brokerage account and 10 shares are held by Mr. Pilmer as custodian.</footnote>
        <footnote id="F2">Does not apply.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Donald Pilmer</signatureName>
        <signatureDate>2016-11-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
