    <SEC-DOCUMENT>0001104659-21-129548-index.html : 20211025
    <SEC-HEADER>0001104659-21-129548.hdr.sgml : 20211025
    <ACCEPTANCE-DATETIME>20211025170616
    ACCESSION NUMBER:		0001104659-21-129548
    CONFORMED SUBMISSION TYPE:	424B3
    PUBLIC DOCUMENT COUNT:		11
    FILED AS OF DATE:		20211025
    DATE AS OF CHANGE:		20211025

    FILER:

    	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

    	FILING VALUES:
    		FORM TYPE:		424B3
    		SEC ACT:		1933 Act
    		SEC FILE NUMBER:	333-259964
    		FILM NUMBER:		211344904

    	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>424B3
    <SEQUENCE>1
    <FILENAME>tm2125387-6_424b3.htm
    <DESCRIPTION>424B3
    <TEXT>
    Document 1 - file: tm2125387-6_424b3.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>2
    <FILENAME>lg_citinoregister-4c.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 2 - file: lg_citinoregister-4c.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>3
    <FILENAME>lg_crowe-4c.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 3 - file: lg_crowe-4c.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>4
    <FILENAME>lg_crowellpindepen-4c.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 4 - file: lg_crowellpindepen-4c.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>5
    <FILENAME>lg_kbfstifel-4clr.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 5 - file: lg_kbfstifel-4clr.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>6
    <FILENAME>lg_oldsecond-4clr.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 6 - file: lg_oldsecond-4clr.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>lg_westsuburban-pn.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 7 - file: lg_westsuburban-pn.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>sg_crowellpnew3-bw.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 8 - file: sg_crowellpnew3-bw.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>sg_jamesleccher-bw.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 9 - file: sg_jamesleccher-bw.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>sg_keefebruwood-bw.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 10 - file: sg_keefebruwood-bw.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>sg_kevinjacker-bw.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 11 - file: sg_kevinjacker-bw.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>