diff --git a/changelogs/fragments/47030-assert-add-success_msg-to-valid-args.yaml b/changelogs/fragments/47030-assert-add-success_msg-to-valid-args.yaml
new file mode 100644
index 00000000000..6027be333d6
--- /dev/null
+++ b/changelogs/fragments/47030-assert-add-success_msg-to-valid-args.yaml
@@ -0,0 +1,2 @@
+bugfixes:
+    - assert - add 'success_msg' to valid args (https://github.com/ansible/ansible/pull/47030)
diff --git a/lib/ansible/plugins/action/assert.py b/lib/ansible/plugins/action/assert.py
index 4028201130d..a3b6af811a3 100644
--- a/lib/ansible/plugins/action/assert.py
+++ b/lib/ansible/plugins/action/assert.py
@@ -27,7 +27,7 @@ class ActionModule(ActionBase):
     ''' Fail with custom message '''
 
     TRANSFERS_FILES = False
-    _VALID_ARGS = frozenset(('fail_msg', 'msg', 'that'))
+    _VALID_ARGS = frozenset(('fail_msg', 'msg', 'success_msg', 'that'))
 
     def run(self, tmp=None, task_vars=None):
         if task_vars is None: