diff --git a/litellm/integrations/otel/model/metadata.py b/litellm/integrations/otel/model/metadata.py
index 28d6ad54607..4f76ebc56d2 100644
--- a/litellm/integrations/otel/model/metadata.py
+++ b/litellm/integrations/otel/model/metadata.py
@@ -152,8 +152,14 @@ class RequestIdentity:
             )
             if (value := get(attr))
         )
+        raw_key_meta: Final = as_str_mapping(get("metadata") or get("user_api_key_auth_metadata"))
+        key_meta: Final = (
+            tuple(flatten_metadata({"user_api_key_auth_metadata": raw_key_meta}))
+            if raw_key_meta is not None
+            else ()
+        )
         request_meta: Final = flatten_metadata(request_metadata) if request_metadata is not None else ()
-        metadata: Final = MappingProxyType(dict((*request_meta, *auth_meta)))
+        metadata: Final = MappingProxyType(dict((*request_meta, *auth_meta, *key_meta)))
         return cls(
             team_id=as_str(get("team_id")),
             team_alias=as_str(get("team_alias")),
diff --git a/tests/unit/integrations/otel/test_otel_v2_sources_of_truth.py b/tests/unit/integrations/otel/test_otel_v2_sources_of_truth.py
index 2d0b4701c9f..4ac00ef889a 100644
--- a/tests/unit/integrations/otel/test_otel_v2_sources_of_truth.py
+++ b/tests/unit/integrations/otel/test_otel_v2_sources_of_truth.py
@@ -1607,6 +1607,18 @@ def test_request_identity_from_user_api_key_auth():
     assert ident.metadata["user_api_key_end_user_id"] == "eu9"
 
 
+def test_request_identity_from_user_api_key_auth_flattens_key_metadata():
+    from litellm.integrations.otel.model.payloads import RequestIdentity
+
+    class _Auth:
+        metadata = {"team": "a", "customtag": "b", "nested": {"k": "v"}}
+
+    ident = RequestIdentity.from_user_api_key_auth(_Auth())
+    assert ident.metadata["user_api_key_auth_metadata.team"] == "a"
+    assert ident.metadata["user_api_key_auth_metadata.customtag"] == "b"
+    assert ident.metadata["user_api_key_auth_metadata.nested.k"] == "v"
+
+
 # --- request-metadata translation layer (RequestContext) -------------------- #