diff --git a/Framework/PythonInterface/mantid/kernel/plugins.py b/Framework/PythonInterface/mantid/kernel/plugins.py
index 602a5850107f..713d88ef8720 100644
--- a/Framework/PythonInterface/mantid/kernel/plugins.py
+++ b/Framework/PythonInterface/mantid/kernel/plugins.py
@@ -13,6 +13,8 @@
 
 import os as _os
 from traceback import format_exc
+import sys
+import importlib.util
 from importlib.machinery import SourceFileLoader
 from . import logger, Logger, config
 
@@ -44,7 +46,16 @@ def run(self):
         name = _os.path.basename(pathname)  # Including extension
         name = _os.path.splitext(name)[0]
         self._logger.debug("Loading python plugin %s" % pathname)
-        return SourceFileLoader(name, pathname).load_module()
+        loader = SourceFileLoader(name, pathname)
+        spec = importlib.util.spec_from_loader(name, loader)
+        module = importlib.util.module_from_spec(spec)
+        loader.exec_module(module)
+        # It's better to let import handle editing sys.modules, but this code used to call
+        # load_module, which would edit sys.modules, but now load_module is deprecated.
+        # We edit sys.modules here so that legacy user scripts will not have to be
+        # edited in order to keep working.
+        sys.modules[name] = module
+        return module
 
 
 # ======================================================================================================================
diff --git a/Framework/PythonInterface/test/python/mantid/kernel/ConfigServiceTest.py b/Framework/PythonInterface/test/python/mantid/kernel/ConfigServiceTest.py
index ced0f26bc87b..40c8c79b01ac 100644
--- a/Framework/PythonInterface/test/python/mantid/kernel/ConfigServiceTest.py
+++ b/Framework/PythonInterface/test/python/mantid/kernel/ConfigServiceTest.py
@@ -5,7 +5,6 @@
 #   NScD Oak Ridge National Laboratory, European Spallation Source,
 #   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
 # SPDX - License - Identifier: GPL - 3.0 +
-import inspect
 import os
 import sys
 import testhelpers
@@ -142,7 +141,7 @@ def test_log_level_get_set(self):
 
     def test_properties_documented(self):
         # location of the rst file relative to this file this will break if either moves
-        doc_filename = os.path.split(inspect.getfile(self.__class__))[0]
+        doc_filename = os.path.split(__file__)[0]
         doc_filename = os.path.join(doc_filename, "../../../../../../docs/source/concepts/PropertiesFile.rst")
         doc_filename = os.path.abspath(doc_filename)
 
diff --git a/Framework/PythonInterface/test/testhelpers/testrunner.py b/Framework/PythonInterface/test/testhelpers/testrunner.py
index 3955fb249db0..674f61f4652f 100644
--- a/Framework/PythonInterface/test/testhelpers/testrunner.py
+++ b/Framework/PythonInterface/test/testhelpers/testrunner.py
@@ -11,6 +11,7 @@
 It is intended to be used as a launcher script for a given unit test file.
 The reports are output to the current working directory.
 """
+import importlib.util
 from importlib.machinery import SourceFileLoader
 import os
 import sys
@@ -33,7 +34,12 @@ def main(argv):
 
     # Load the test and copy over any module variables so that we have
     # the same environment defined here
-    test_module = SourceFileLoader(module_name(pathname), pathname).load_module()
+
+    test_module_name = module_name(pathname)
+    test_loader = SourceFileLoader(test_module_name, pathname)
+    test_spec = importlib.util.spec_from_loader(test_module_name, test_loader)
+    test_module = importlib.util.module_from_spec(test_spec)
+    test_loader.exec_module(test_module)
     test_module_globals = dir(test_module)
     this_globals = globals()
     for key in test_module_globals:
diff --git a/Testing/SystemTests/lib/systemtests/systemtesting.py b/Testing/SystemTests/lib/systemtests/systemtesting.py
index 44707644a885..4fa5aed48f21 100644
--- a/Testing/SystemTests/lib/systemtests/systemtesting.py
+++ b/Testing/SystemTests/lib/systemtests/systemtesting.py
@@ -1153,18 +1153,14 @@ def loadTestsFromModule(self, filename):
         modname = modname.split(".py")[0]
         tests = []
         try:
-            spec = importlib.util.spec_from_file_location("", filename)
+            spec = importlib.util.spec_from_file_location(modname, filename)
             mod = importlib.util.module_from_spec(spec)
             spec.loader.exec_module(mod)
 
-            mod_attrs = dir(mod)
-            for key in mod_attrs:
-                value = getattr(mod, key)
-                if key == "MantidSystemTest" or not inspect.isclass(value):
-                    continue
-                if self.isValidTestClass(value):
-                    test_name = key
-                    tests.append(TestSuite(self._runner.getTestDir(), modname, test_name, filename))
+            module_classes = dict(inspect.getmembers(mod, inspect.isclass))
+            module_classes = [x for x in module_classes if self.isValidTestClass(module_classes[x]) and x != "MantidSystemTest"]
+            for test_name in module_classes:
+                tests.append(TestSuite(self._runner.getTestDir(), modname, test_name, filename))
             module_loaded = True
         except Exception:
             print("Error importing module '{}':".format(modname))
diff --git a/Testing/Tools/cxxtest/sample/SCons/SConstruct b/Testing/Tools/cxxtest/sample/SCons/SConstruct
index 58e661efe546..308176e17d09 100644
--- a/Testing/Tools/cxxtest/sample/SCons/SConstruct
+++ b/Testing/Tools/cxxtest/sample/SCons/SConstruct
@@ -6,8 +6,14 @@ cxxtest_path = '../..'
 # without having to copy it into a particular path.
 # for nicer examples you *should* use, see the cxxtest builder tests in the
 # build_tools/SCons/test directory.
+import importlib.util
 from importlib.machinery import SourceFileLoader
-cxxtest = SourceFileLoader('cxxtest', cxxtestbuilder_path).load_module()
+
+cxxtest_name = 'cxxtest'
+loader = SourceFileLoader(cxxtest_name, cxxtestbuilder_path)
+spec = importlib.util.spec_from_loader(cxxtest_name, loader)
+cxxtest = importlib.util.module_from_spec(spec)
+loader.exec_module(cxxtest)
 
 # First build the 'real' library, when working on an embedded system
 # this may involve a cross compiler.
diff --git a/Testing/Tools/cxxtest/test/unit/SConstruct b/Testing/Tools/cxxtest/test/unit/SConstruct
index 1da2323dd7b2..13108f0f6162 100644
--- a/Testing/Tools/cxxtest/test/unit/SConstruct
+++ b/Testing/Tools/cxxtest/test/unit/SConstruct
@@ -2,8 +2,14 @@ CxxTestBuilder_path = '../../build_tools/SCons/cxxtest.py'
 CxxTest_dir = '../..'
 
 # First a little python magic to pull in CxxTestBuilder
+import importlib.util
 from importlib.machinery import SourceFileLoader
-cxxtest = SourceFileLoader('cxxtest', CxxTestBuilder_path).load_module()
+
+cxxtest_name = 'cxxtest'
+loader = SourceFileLoader(cxxtest_name, CxxTestBuilder_path)
+spec = importlib.util.spec_from_loader(cxxtest_name, loader)
+cxxtest = importlib.util.module_from_spec(spec)
+loader.exec_module(cxxtest)
 env = Environment()
 cxxtest.generate(env, CXXTEST_INSTALL_DIR=CxxTest_dir)
 
diff --git a/docs/source/release/v6.11.0/Framework/Python/Bugfixes/37031.rst b/docs/source/release/v6.11.0/Framework/Python/Bugfixes/37031.rst
new file mode 100644
index 000000000000..c9be694da7db
--- /dev/null
+++ b/docs/source/release/v6.11.0/Framework/Python/Bugfixes/37031.rst
@@ -0,0 +1 @@
+- Fixed error in the log about `load_module()` being deprecated in Python 3.12.
\ No newline at end of file