diff --git a/lib/crewai/src/crewai/llms/providers/gemini/completion.py b/lib/crewai/src/crewai/llms/providers/gemini/completion.py
index b099fe2373..122f31ad7f 100644
--- a/lib/crewai/src/crewai/llms/providers/gemini/completion.py
+++ b/lib/crewai/src/crewai/llms/providers/gemini/completion.py
@@ -9,6 +9,7 @@
 
 from pydantic import BaseModel, Field, PrivateAttr, model_validator
 
+from crewai import __version__
 from crewai.events.types.llm_events import LLMCallType
 from crewai.llms.base_llm import BaseLLM, llm_call_context
 from crewai.llms.hooks.base import BaseInterceptor
@@ -181,11 +182,24 @@ def _initialize_client(self, use_vertexai: bool = False) -> genai.Client:
             When vertexai=True is set, it routes to aiplatform.googleapis.com which rejects
             API keys. Use Gemini API endpoint for API key authentication instead.
         """
-        client_params = {}
+        client_params: dict[str, Any] = {}
 
         if self.client_params:
             client_params.update(self.client_params)
 
+        http_options = client_params.get("http_options")
+        if http_options is None:
+            http_options = types.HttpOptions()
+        elif isinstance(http_options, dict):
+            http_options = types.HttpOptions(**http_options)
+
+        if not http_options.headers:
+            http_options.headers = {"user-agent": f"crewai/{__version__}"}
+        elif "user-agent" not in http_options.headers:
+            http_options.headers["user-agent"] = f"crewai/{__version__}"
+
+        client_params["http_options"] = http_options
+
         has_api_key = bool(self.api_key)
         has_project = bool(self.project)
 
@@ -215,7 +229,7 @@ def _initialize_client(self, use_vertexai: bool = False) -> genai.Client:
             # See: https://cloud.google.com/vertex-ai/generative-ai/docs/start/quickstart?usertype=apikey
             if use_vertexai:
                 client_params["vertexai"] = True
-                client_params["http_options"] = types.HttpOptions(api_version="v1")
+                client_params["http_options"].api_version = "v1"
             else:
                 # This ensures we use the Gemini API (generativelanguage.googleapis.com)
                 client_params["vertexai"] = False
diff --git a/lib/crewai/tests/llms/google/test_google.py b/lib/crewai/tests/llms/google/test_google.py
index 2c03dcd23b..6b5005abf7 100644
--- a/lib/crewai/tests/llms/google/test_google.py
+++ b/lib/crewai/tests/llms/google/test_google.py
@@ -122,6 +122,67 @@ def test_gemini_completion_initialization_parameters():
     assert llm.top_k == 40
 
 
+def test_gemini_user_agent_header_default():
+    """Test that default Gemini client initialization sets the user-agent header."""
+    from crewai import __version__
+    from crewai.llms.providers.gemini.completion import GeminiCompletion
+
+    llm = GeminiCompletion(model="gemini-3.7-flash", api_key="test-key")
+    client = llm._get_sync_client()
+    assert client._api_client._http_options is not None
+    assert client._api_client._http_options.headers is not None
+    assert f"crewai/{__version__}" in client._api_client._http_options.headers["user-agent"]
+
+
+def test_gemini_http_options_dict_conversion():
+    """Test that dictionary http_options in client_params are converted to types.HttpOptions."""
+    from crewai import __version__
+    from crewai.llms.providers.gemini.completion import GeminiCompletion
+
+    llm = GeminiCompletion(
+        model="gemini-3.7-flash",
+        api_key="test-key",
+        client_params={"http_options": {"timeout": 45}},
+    )
+    client = llm._get_sync_client()
+    assert client._api_client._http_options is not None
+    assert client._api_client._http_options.timeout == 45
+    assert f"crewai/{__version__}" in client._api_client._http_options.headers["user-agent"]
+
+
+def test_gemini_http_options_custom_headers_preserved():
+    """Test that custom headers in types.HttpOptions are preserved alongside user-agent."""
+    from google.genai import types
+    from crewai import __version__
+    from crewai.llms.providers.gemini.completion import GeminiCompletion
+
+    llm = GeminiCompletion(
+        model="gemini-3.7-flash",
+        api_key="test-key",
+        client_params={"http_options": types.HttpOptions(headers={"X-Custom-Header": "my-value"})},
+    )
+    client = llm._get_sync_client()
+    assert client._api_client._http_options is not None
+    assert client._api_client._http_options.headers.get("X-Custom-Header") == "my-value"
+    assert f"crewai/{__version__}" in client._api_client._http_options.headers["user-agent"]
+
+
+def test_gemini_vertex_express_mode_preserves_user_agent():
+    """Test that Vertex AI Express mode sets api_version='v1' and preserves user-agent."""
+    from crewai import __version__
+    from crewai.llms.providers.gemini.completion import GeminiCompletion
+
+    llm = GeminiCompletion(
+        model="gemini-3.7-flash",
+        api_key="test-key",
+        use_vertexai=True,
+    )
+    client = llm._get_sync_client()
+    assert client._api_client._http_options is not None
+    assert client._api_client._http_options.api_version == "v1"
+    assert f"crewai/{__version__}" in client._api_client._http_options.headers["user-agent"]
+
+
 def test_gemini_started_event_surfaces_max_output_tokens():
     from crewai.events.event_bus import crewai_event_bus
     from crewai.events.types.llm_events import LLMCallStartedEvent