<?xml version="1.0" encoding="utf-8"?>
<!--XBRL document created with Toppan Merrill Bridge  10.5.0.8 -->
<!--Based on XBRL 2.1-->
<!--Created on: 1/24/2024 8:37:45 PM-->
<!--Modified on: 1/24/2024 8:37:45 PM-->
<xsd:schema targetNamespace="http://www.OldSecondBancorp.com/20240124" attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:us-gaap="http://fasb.org/us-gaap/2023" xmlns:srt-types="http://fasb.org/srt-types/2023" xmlns:us-roles="http://fasb.org/us-roles/2023" xmlns:ref="http://www.xbrl.org/2006/ref" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:currency="http://xbrl.sec.gov/currency/2023" xmlns:xl="http://www.xbrl.org/2003/XLink" xmlns:naics="http://xbrl.sec.gov/naics/2023" xmlns:srt-roles="http://fasb.org/srt-roles/2023" xmlns:country="http://xbrl.sec.gov/country/2023" xmlns:utr="http://www.xbrl.org/2009/utr" xmlns:srt="http://fasb.org/srt/2023" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:exch="http://xbrl.sec.gov/exch/2023" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:sic="http://xbrl.sec.gov/sic/2023" xmlns:us-types="http://fasb.org/us-types/2023" xmlns:negated="http://www.xbrl.org/2009/role/negated" xmlns:attributeFormDefault="unqualified" xmlns:stpr="http://xbrl.sec.gov/stpr/2023" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2022-03-31" xmlns:deprecated="http://www.xbrl.org/2009/role/deprecated" xmlns:net="http://www.xbrl.org/2009/role/net" xmlns:dei="http://xbrl.sec.gov/dei/2023" xmlns:dtr="http://www.xbrl.org/2009/dtr" xmlns:cef="http://xbrl.sec.gov/cef/2023" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns:osbc="http://www.OldSecondBancorp.com/20240124" xmlns:cef-pre="http://xbrl.sec.gov/cef-pre/2023">
  <xsd:annotation>
    <xsd:appinfo>
      <link:roleType roleURI="http://www.OldSecondBancorp.com/role/DocumentDocumentAndEntityInformation" id="DocumentDocumentAndEntityInformation">
        <link:definition>00090 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbaseRef xlink:type="simple" xlink:href="tmb-20240124_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="tmb-20240124_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:import namespace="http://xbrl.sec.gov/cef/2023" schemaLocation="https://xbrl.sec.gov/cef/2023/cef-2023.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/dei/2023" schemaLocation="https://xbrl.sec.gov/dei/2023/dei-2023.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/cef-pre/2023" schemaLocation="https://xbrl.sec.gov/cef/2023/cef-2023_pre.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/2022-03-31" schemaLocation="https://www.xbrl.org/dtr/type/2022-03-31/types.xsd" />
  <xsd:element name="DocumentAndEntityInformationAbstract" id="osbc_DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
</xsd:schema>
