diff --git a/‎gitlab/v4/cli.py‎
Lines changed: 11 additions & 5 deletions b/‎gitlab/v4/cli.py‎
Lines changed: 11 additions & 5 deletions
@@ -200,11 +200,15 @@ def _populate_sub_parser_by_class(
     mgr_cls_name = f"{cls.__name__}Manager"
     mgr_cls = getattr(gitlab.v4.objects, mgr_cls_name)
 
-    for action_name in ["list", "get", "create", "update", "delete"]:
+    ACTIONS = ("list", "get", "create", "update", "delete")
+    action_parsers = set()
+
+    for action_name in ACTIONS:
         if not hasattr(mgr_cls, action_name):
             continue
 
         sub_parser_action = sub_parser.add_parser(action_name)
+        action_parsers.add(action_name)
         sub_parser_action.add_argument("--sudo", required=False)
         if mgr_cls._from_parent_attrs:
             for x in mgr_cls._from_parent_attrs:
@@ -268,6 +272,9 @@ def _populate_sub_parser_by_class(
     if cls.__name__ in cli.custom_actions:
         name = cls.__name__
         for action_name in cli.custom_actions[name]:
+            if action_name in action_parsers:
+                continue
+
             sub_parser_action = sub_parser.add_parser(action_name)
             # Get the attributes for URL/path construction
             if mgr_cls._from_parent_attrs:
@@ -326,16 +333,15 @@ def extend_parser(parser: argparse.ArgumentParser) -> argparse.ArgumentParser:
     subparsers.required = True
 
     # populate argparse for all Gitlab Object
-    classes = []
+    classes = set()
     for cls in gitlab.v4.objects.__dict__.values():
         if not isinstance(cls, type):
             continue
         if issubclass(cls, gitlab.base.RESTManager):
             if cls._obj_cls is not None:
-                classes.append(cls._obj_cls)
-    classes.sort(key=operator.attrgetter("__name__"))
+                classes.add(cls._obj_cls)
 
-    for cls in classes:
+    for cls in sorted(classes, key=operator.attrgetter("__name__")):
         arg_name = cli.cls_to_what(cls)
         object_group = subparsers.add_parser(arg_name)