<SEC-DOCUMENT>0001179110-20-001808.txt : 20200219
<SEC-HEADER>0001179110-20-001808.hdr.sgml : 20200219
<ACCEPTANCE-DATETIME>20200219151157
ACCESSION NUMBER:		0001179110-20-001808
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20200218
FILED AS OF DATE:		20200219
DATE AS OF CHANGE:		20200219

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Ladowicz John
		CENTRAL INDEX KEY:			0001424453

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-10537
		FILM NUMBER:		20629227

	MAIL ADDRESS:	
		STREET 1:		20201 S. LAGRANGE RD., STE 100
		CITY:			FRANKFORT
		STATE:			IL
		ZIP:			60423

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:			1231

	BUSINESS ADDRESS:	
		STREET 1:		37 S RIVER ST
		CITY:			AURORA
		STATE:			IL
		ZIP:			60507
		BUSINESS PHONE:		6308920202

	MAIL ADDRESS:	
		STREET 1:		37 SOUTH RIVER STREET
		CITY:			AURORA
		STATE:			IL
		ZIP:			60507
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-02-18</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001424453</rptOwnerCik>
            <rptOwnerName>Ladowicz John</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>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Old Second Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-02-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1500</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>23146</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Old Second Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>234277</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>IRA</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Included in this total are 11,146 shares in Mr. Ladowicz' name outright, 7,000 shares of restricted stock units and 5,000 shares of Performance Based restricted stock units in Mr. Ladowicz' name.</footnote>
        <footnote id="F2">Does not apply.</footnote>
        <footnote id="F3">These shares represent Restricted Stock Units granted pursuant to the 2019 Long Term Equity Incentive Plan. These shares have a 3-year cliff vesting.</footnote>
        <footnote id="F4">These shares represent 14,427 shares in a traditional IRA and 219,850 shares in a Roth IRA, both in Mr. Ladowicz's name. The original number of shares reported by the Plan Trustee included shares held in Trust Accounts by family members with no controlling interest by Mr. Ladowicz.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ John Ladowicz</signatureName>
        <signatureDate>2020-02-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
