diff --git a/admin/tool/uploaduser/classes/process.php b/admin/tool/uploaduser/classes/process.php
index 6d9cdc53bb1..c3820a4fa12 100644
--- a/admin/tool/uploaduser/classes/process.php
+++ b/admin/tool/uploaduser/classes/process.php
@@ -1384,8 +1384,14 @@ class process {
                 }
             }
         }
+
+        // Warn user about invalid data values.
         if (($invalid = \core_user::validate($user)) !== true) {
-            $this->upt->track('status', get_string('invaliduserdata', 'tool_uploaduser', s($user->username)), 'warning');
+            $listseparator = get_string('listsep', 'langconfig') . ' ';
+            $this->upt->track('status', get_string('invaliduserdatavalues', 'tool_uploaduser', [
+                'username' => s($user->username),
+                'values' => implode($listseparator, array_keys($invalid)),
+            ]), 'warning');
         }
     }
 
diff --git a/admin/tool/uploaduser/lang/en/tool_uploaduser.php b/admin/tool/uploaduser/lang/en/tool_uploaduser.php
index 7c480398eb1..e0c8987d82c 100644
--- a/admin/tool/uploaduser/lang/en/tool_uploaduser.php
+++ b/admin/tool/uploaduser/lang/en/tool_uploaduser.php
@@ -50,6 +50,7 @@ The example text file may also be used for testing, as you are able to preview u
 $string['infoprefix'] = 'Info:';
 $string['invalidupdatetype'] = 'This option cannot be selected with the chosen upload type.';
 $string['invaliduserdata'] = 'Invalid data detected for user {$a} and it has been automatically cleaned.';
+$string['invaliduserdatavalues'] = 'Invalid data detected for user \'{$a->username}\' ({$a->values}), which has been automatically cleaned.';
 $string['invalidtheme'] = 'Theme "{$a}" is not installed and will be ignored.';
 $string['linex'] = 'Line {$a}';
 $string['matchemail'] = 'Match on email address';
diff --git a/admin/tool/uploaduser/tests/upload_users_test.php b/admin/tool/uploaduser/tests/upload_users_test.php
index 49e204e716f..559f19ca4c6 100644
--- a/admin/tool/uploaduser/tests/upload_users_test.php
+++ b/admin/tool/uploaduser/tests/upload_users_test.php
@@ -186,6 +186,26 @@ EOF;
         $this->assertEquals('student1', reset($usersasdefaultrole)->username);
     }
 
+    /**
+     * Test that invalid data contained in uploaded CSV triggers appropriate warnings
+     */
+    public function test_user_upload_user_validate(): void {
+        $this->resetAfterTest();
+        $this->setAdminUser();
+
+        $csv = <<<EOF
+username,firstname,lastname,email,country
+student1,Student,One,s1@example.com,Wales
+EOF;
+
+        $output = $this->process_csv_upload($csv, ['--uutype=' . UU_USER_ADDNEW]);
+
+        // We should get the debugging from the user class itself, as well as warning in the output regarding the same.
+        $this->assertDebuggingCalled('The property \'country\' has invalid data and has been cleaned.');
+        $this->assertStringContainsString('Invalid data detected for user \'student1\' (country), ' .
+            'which has been automatically cleaned.', $output);
+    }
+
     /**
      * Generate cli_helper and mock $_SERVER['argv']
      *