<SEC-DOCUMENT>0001415889-25-020082.txt : 20250721
<SEC-HEADER>0001415889-25-020082.hdr.sgml : 20250721
<ACCEPTANCE-DATETIME>20250721175613
ACCESSION NUMBER:		0001415889-25-020082
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250718
FILED AS OF DATE:		20250721
DATE AS OF CHANGE:		20250721

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Campbell Darin Patrick
		CENTRAL INDEX KEY:			0002074132
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-10537
		FILM NUMBER:		251138239

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

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			OLD SECOND BANCORP INC
		CENTRAL INDEX KEY:			0000357173
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		ORGANIZATION NAME:           	02 Finance
		EIN:				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>form4-07212025_090707.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-07-18</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002074132</rptOwnerCik>
            <rptOwnerName>Campbell Darin Patrick</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>true</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>President, Powersports Lending</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Old second Bancorp Inc., Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-07-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>57565</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>57565</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>IRA</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Old Second Bancorp, Inc. Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>309680</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These shares were issuable pursuant to the merger of Bancorp Financial, Inc. with and into Old Second Bancorp, Inc., which became effective on July 1, 2025. The reporting person held 22,300 shares of Bancorp Financial, Inc., which pursuant to the merger agreement was converted into 57,565 shares of Old Second Bancorp, Inc. common stock. These shares are held in a custodial account in an IRA on behalf of the reporting person. The exchange of shares occurred on July 19, 2025.</footnote>
        <footnote id="F2">These securities are issuable pursuant to the merger of Bancorp Financial, Inc. with and into Old Second Bancorp, Inc., which became effective on July 1, 2025. The reporting person held 119,966 shares of Bancorp Financial, Inc., which pursuant to the merger agreement, will be converted into 309,680 shares of Old Second Bancorp, Inc. common stock. The exchange of shares has not yet occurred, but the right to receive the shares is fixed and irrevocable under the merger agreement. The exchange of shares occurred on July 18, 2025.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Shirley Cantrell, Attorney-in-Fact</signatureName>
        <signatureDate>2025-07-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
