diff --git a/src/google/adk/tools/agent_tool.py b/src/google/adk/tools/agent_tool.py
index 46d8616619..5f1bcadb75 100644
--- a/src/google/adk/tools/agent_tool.py
+++ b/src/google/adk/tools/agent_tool.py
@@ -188,7 +188,12 @@ async def run_async(
 
     if not last_content:
       return ''
-    merged_text = '\n'.join(p.text for p in last_content.parts if p.text)
+    parts = last_content.parts or []
+    merged_text = '\n'.join(
+        p.text
+        for p in parts
+        if p.text
+    )
     if isinstance(self.agent, LlmAgent) and self.agent.output_schema:
       tool_result = self.agent.output_schema.model_validate_json(
           merged_text
diff --git a/src/google/adk/tools/google_search_agent_tool.py b/src/google/adk/tools/google_search_agent_tool.py
index 77cb6fedf9..c67faae6f1 100644
--- a/src/google/adk/tools/google_search_agent_tool.py
+++ b/src/google/adk/tools/google_search_agent_tool.py
@@ -125,7 +125,12 @@ async def run_async(
 
     if not last_content:
       return ''
-    merged_text = '\n'.join(p.text for p in last_content.parts if p.text)
+    parts = last_content.parts or []
+    merged_text = '\n'.join(
+        p.text
+        for p in parts
+        if p.text
+    )
     if isinstance(self.agent, LlmAgent) and self.agent.output_schema:
       tool_result = self.agent.output_schema.model_validate_json(
           merged_text
diff --git a/tests/unittests/tools/test_google_search_agent_tool_repro.py b/tests/unittests/tools/test_google_search_agent_tool_repro.py
new file mode 100644
index 0000000000..644de631a9
--- /dev/null
+++ b/tests/unittests/tools/test_google_search_agent_tool_repro.py
@@ -0,0 +1,58 @@
+from google.adk.agents.invocation_context import InvocationContext
+from google.adk.agents.llm_agent import Agent
+from google.adk.models.llm_response import LlmResponse
+from google.adk.sessions.in_memory_session_service import InMemorySessionService
+from google.adk.tools.google_search_agent_tool import GoogleSearchAgentTool
+from google.adk.tools.tool_context import ToolContext
+from google.genai import types
+from google.genai.types import Part
+from pytest import mark
+
+from .. import testing_utils
+
+function_call_no_schema = Part.from_function_call(
+    name='tool_agent', args={'request': 'test1'}
+)
+
+
+@mark.asyncio
+async def test_run_async_handles_none_parts_in_response():
+  """Verify run_async handles None parts in the response without crashing."""
+
+  # Mock model for the tool_agent that returns content with parts=None
+  # This simulates the condition causing the TypeError
+  tool_agent_model = testing_utils.MockModel.create(
+      responses=[
+          LlmResponse(
+              content=types.Content(parts=None),
+          )
+      ]
+  )
+
+  tool_agent = Agent(
+      name='tool_agent',
+      model=tool_agent_model,
+  )
+
+  agent_tool = GoogleSearchAgentTool(agent=tool_agent)
+
+  session_service = InMemorySessionService()
+  session = await session_service.create_session(
+      app_name='test_app', user_id='test_user'
+  )
+
+  invocation_context = InvocationContext(
+      invocation_id='invocation_id',
+      agent=tool_agent,
+      session=session,
+      session_service=session_service,
+  )
+  tool_context = ToolContext(invocation_context=invocation_context)
+
+  # This should not raise TypeError: 'NoneType' object is not iterable
+  # It should ideally return an empty string or handle it gracefully
+  tool_result = await agent_tool.run_async(
+      args=function_call_no_schema.function_call.args, tool_context=tool_context
+  )
+
+  assert tool_result == ''