diff --git a/src/google/adk/models/lite_llm.py b/src/google/adk/models/lite_llm.py
index 3a6c36624d..27c31dd542 100644
--- a/src/google/adk/models/lite_llm.py
+++ b/src/google/adk/models/lite_llm.py
@@ -2168,7 +2168,7 @@ class LiteLlm(BaseLlm):
     llm_client: The LLM client to use for the model.
   """
 
-  llm_client: LiteLLMClient = Field(default_factory=LiteLLMClient)
+  llm_client: LiteLLMClient = Field(default_factory=LiteLLMClient, exclude=True)
   """The LLM client to use for the model."""
 
   _additional_args: Dict[str, Any] = None
diff --git a/tests/unittests/models/test_litellm.py b/tests/unittests/models/test_litellm.py
index 9007bcf201..7a93bdf773 100644
--- a/tests/unittests/models/test_litellm.py
+++ b/tests/unittests/models/test_litellm.py
@@ -4954,3 +4954,10 @@ async def test_content_to_message_param_anthropic_no_signature_falls_back():
   # Falls back to reasoning_content when no signatures present
   assert result.get("reasoning_content") == "thinking without sig"
   assert "thinking_blocks" not in result
+
+
+def test_lite_llm_model_dump_excludes_llm_client():
+  """llm_client should not appear in model_dump output (not JSON serializable)."""
+  model = LiteLlm(model="openrouter/openai/gpt-4o-mini")
+  dumped = model.model_dump(mode="python", exclude_none=True)
+  assert "llm_client" not in dumped