diff --git a/src/senaite/core/catalog/indexer/configure.zcml b/src/senaite/core/catalog/indexer/configure.zcml
index 46ebfd713f..5edbe1a891 100644
--- a/src/senaite/core/catalog/indexer/configure.zcml
+++ b/src/senaite/core/catalog/indexer/configure.zcml
@@ -30,6 +30,9 @@
   <!-- AnalysisCategory Indexer -->
   <adapter name="sortable_title" factory=".analysiscategory.sortable_title"/>
 
+  <!-- SubGroup Indexer -->
+  <adapter name="sortable_title" factory=".subgroup.sortable_title"/>
+
   <!-- ARReport Indexer -->
   <adapter name="sample_uid" factory=".arreport.sample_uid"/>
   <adapter name="arreport_searchable_text" factory=".arreport.arreport_searchable_text"/>
diff --git a/src/senaite/core/catalog/indexer/subgroup.py b/src/senaite/core/catalog/indexer/subgroup.py
new file mode 100644
index 0000000000..2c79f4b428
--- /dev/null
+++ b/src/senaite/core/catalog/indexer/subgroup.py
@@ -0,0 +1,32 @@
+# -*- coding: utf-8 -*-
+#
+# This file is part of SENAITE.CORE.
+#
+# SENAITE.CORE is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, version 2.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+# details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc., 51
+# Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+#
+# Copyright 2018-2024 by it's authors.
+# Some rights reserved, see README and LICENSE.
+
+from plone.indexer import indexer
+from Products.CMFPlone.utils import safe_callable
+from senaite.core.catalog.utils import sortable_sortkey_title
+from senaite.core.interfaces import ISubGroup
+
+
+@indexer(ISubGroup)
+def sortable_title(instance):
+    title = sortable_sortkey_title(instance)
+    if safe_callable(title):
+        title = title()
+    return title
diff --git a/src/senaite/core/content/subgroup.py b/src/senaite/core/content/subgroup.py
index b99e0c3324..823ba75f3c 100644
--- a/src/senaite/core/content/subgroup.py
+++ b/src/senaite/core/content/subgroup.py
@@ -27,7 +27,9 @@
 from senaite.core.content.base import Container
 from senaite.core.interfaces import ISubGroup
 from zope import schema
+from zope.interface import Invalid
 from zope.interface import implementer
+from zope.interface import invariant
 
 
 class ISubGroupSchema(model.Schema):
@@ -50,14 +52,36 @@ class ISubGroupSchema(model.Schema):
         required=False,
     )
 
-    sort_key = schema.TextLine(
+    sort_key = schema.Float(
         title=_(
-            "title_subgroup_sortkey",
+            "title_subgroup_sort_key",
             default="Sort Key"
         ),
+        description=_(
+            u"description_subgroup_sort_key",
+            default=u"Float value from 0.0 - 1000.0 indicating the sort order."
+                    " Duplicate values are ordered alphabetically.",
         required=False,
     )
 
+    @invariant
+    def validate_sort_key(data):
+        """Checks sort_key field for float value if exist
+        """
+        sort_key = getattr(data, "sort_key", None)
+        if sort_key is None:
+            return
+
+        try:
+            value = float(data.sort_key)
+        except Exception:
+            msg = _("Validation failed: value must be float")
+            raise Invalid(msg)
+
+        if value < 0 or value > 1000:
+            msg = _("Validation failed: value must be between 0 and 1000")
+            raise Invalid(msg)
+
 
 @implementer(ISubGroup, ISubGroupSchema, IDeactivable)
 class SubGroup(Container):
diff --git a/src/senaite/core/profiles/default/metadata.xml b/src/senaite/core/profiles/default/metadata.xml
index 4165d6b115..8db0af2159 100644
--- a/src/senaite/core/profiles/default/metadata.xml
+++ b/src/senaite/core/profiles/default/metadata.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <metadata>
-  <version>2655</version>
+  <version>2656</version>
   <dependencies>
     <dependency>profile-Products.ATContentTypes:base</dependency>
     <dependency>profile-Products.CMFEditions:CMFEditions</dependency>
diff --git a/src/senaite/core/upgrade/v02_06_000.py b/src/senaite/core/upgrade/v02_06_000.py
index 133854fa15..e02c51200a 100644
--- a/src/senaite/core/upgrade/v02_06_000.py
+++ b/src/senaite/core/upgrade/v02_06_000.py
@@ -2725,3 +2725,13 @@ def reindex_specs(tool):
         logger.info("Reindex analysis spec: %r" % obj)
         obj.reindexObject(idxs=["sampletype_uid", "sampletype_title"])
     logger.info("Reindexing analysis specifications [DONE]")
+
+
+def reindex_sub_groups(tool):
+    logger.info("Reindexing sub group ...")
+    cat = api.get_tool(SETUP_CATALOG)
+    for brain in cat(portal_type="SubGroup"):
+        obj = brain.getObject()
+        logger.info("Reindex sub group: %r" % obj)
+        obj.reindexObject(idxs=["sortable_title"], update_metadata=False)
+    logger.info("Reindexing sub groups [DONE]")
diff --git a/src/senaite/core/upgrade/v02_06_000.zcml b/src/senaite/core/upgrade/v02_06_000.zcml
index bd99dfef63..9365758f56 100644
--- a/src/senaite/core/upgrade/v02_06_000.zcml
+++ b/src/senaite/core/upgrade/v02_06_000.zcml
@@ -3,6 +3,14 @@
     xmlns:genericsetup="http://namespaces.zope.org/genericsetup"
     i18n_domain="senaite.core">
 
+  <genericsetup:upgradeStep
+      title="SENAITE.CORE 2.6.0: Fix subgroups not sorted by sort key"
+      description="Reindex sortable_title for all sub groups"
+      source="2655"
+      destination="2656"
+      handler=".v02_06_000.reindex_sub_groups"
+      profile="senaite.core:default"/>
+
   <genericsetup:upgradeStep
       title="SENAITE.CORE 2.6.0: Fix sampletype-related indexes for specs"
       description="SampleType-specific indexes Analysis Specs are not indexed"