diff --git a/src/google/adk/cli/utils/agent_loader.py b/src/google/adk/cli/utils/agent_loader.py
index 8b5805c5a9..efd24648dc 100644
--- a/src/google/adk/cli/utils/agent_loader.py
+++ b/src/google/adk/cli/utils/agent_loader.py
@@ -335,13 +335,18 @@ def load_agent(self, agent_name: str) -> Union[BaseAgent, App]:
   def list_agents(self) -> list[str]:
     """Lists all agents available in the agent loader (sorted alphabetically)."""
     base_path = Path.cwd() / self.agents_dir
-    agent_names = [
-        x
-        for x in os.listdir(base_path)
-        if os.path.isdir(os.path.join(base_path, x))
-        and not x.startswith(".")
-        and x != "__pycache__"
-    ]
+    agent_names = []
+    for x in os.listdir(base_path):
+      if (
+          os.path.isdir(os.path.join(base_path, x))
+          and not x.startswith(".")
+          and x != "__pycache__"
+      ):
+        try:
+          self._determine_agent_language(x)
+          agent_names.append(x)
+        except ValueError:
+          continue
     agent_names.sort()
     return agent_names
 
diff --git a/tests/unittests/cli/utils/test_agent_loader.py b/tests/unittests/cli/utils/test_agent_loader.py
index f3eb33969a..0a7f9fc04f 100644
--- a/tests/unittests/cli/utils/test_agent_loader.py
+++ b/tests/unittests/cli/utils/test_agent_loader.py
@@ -993,3 +993,48 @@ def __init__(self):
       assert len(detailed_list) == 1
       assert detailed_list[0]["name"] == agent_name
       assert not detailed_list[0]["is_computer_use"]
+
+  def test_list_agents_excludes_non_agent_directories(self):
+    """Test that list_agents filters out directories without agent definitions."""
+    with tempfile.TemporaryDirectory() as temp_dir:
+      temp_path = Path(temp_dir)
+
+      valid_package = temp_path / "valid_agent"
+      valid_package.mkdir()
+      (valid_package / "__init__.py").write_text(dedent("""
+          from google.adk.agents.base_agent import BaseAgent
+
+          class ValidAgent(BaseAgent):
+              def __init__(self):
+                  super().__init__(name="valid_agent")
+
+          root_agent = ValidAgent()
+      """))
+
+      valid_module = temp_path / "module_agent"
+      valid_module.mkdir()
+      (valid_module / "agent.py").write_text(dedent("""
+          from google.adk.agents.base_agent import BaseAgent
+
+          class ModuleAgent(BaseAgent):
+              def __init__(self):
+                  super().__init__(name="module_agent")
+
+          root_agent = ModuleAgent()
+      """))
+
+      valid_yaml = temp_path / "yaml_agent"
+      valid_yaml.mkdir()
+      (valid_yaml / "root_agent.yaml").write_text("name: yaml_agent\n")
+
+      (temp_path / "random_folder").mkdir()
+      (temp_path / "data").mkdir()
+      (temp_path / "tmp").mkdir()
+
+      loader = AgentLoader(str(temp_path))
+      agents = loader.list_agents()
+
+      assert agents == ["module_agent", "valid_agent", "yaml_agent"]
+      assert "random_folder" not in agents
+      assert "data" not in agents
+      assert "tmp" not in agents