diff --git a/src/google/adk/models/apigee_llm.py b/src/google/adk/models/apigee_llm.py
index 0229f976..0d533a67 100644
--- a/src/google/adk/models/apigee_llm.py
+++ b/src/google/adk/models/apigee_llm.py
@@ -37,6 +37,8 @@ logger = logging.getLogger('google_adk.' + __name__)
 
 _APIGEE_PROXY_URL_ENV_VARIABLE_NAME = 'APIGEE_PROXY_URL'
 _GOOGLE_GENAI_USE_VERTEXAI_ENV_VARIABLE_NAME = 'GOOGLE_GENAI_USE_VERTEXAI'
+_PROJECT_ENV_VARIABLE_NAME = 'GOOGLE_CLOUD_PROJECT'
+_LOCATION_ENV_VARIABLE_NAME = 'GOOGLE_CLOUD_LOCATION'
 
 
 class ApigeeLlm(Gemini):
@@ -90,6 +92,24 @@ class ApigeeLlm(Gemini):
       raise ValueError(f'Invalid model string: {model}')
 
     self._isvertexai = _identify_vertexai(model)
+
+    # Set the project and location for Vertex AI.
+    if self._isvertexai:
+      self._project = os.environ.get(_PROJECT_ENV_VARIABLE_NAME)
+      self._location = os.environ.get(_LOCATION_ENV_VARIABLE_NAME)
+
+      if not self._project:
+        raise ValueError(
+            f'The {_PROJECT_ENV_VARIABLE_NAME} environment variable must be'
+            ' set.'
+        )
+
+      if not self._location:
+        raise ValueError(
+            f'The {_LOCATION_ENV_VARIABLE_NAME} environment variable must be'
+            ' set.'
+        )
+
     self._api_version = _identify_api_version(model)
     self._proxy_url = proxy_url or os.environ.get(
         _APIGEE_PROXY_URL_ENV_VARIABLE_NAME
@@ -128,9 +148,15 @@ class ApigeeLlm(Gemini):
         **kwargs_for_http_options,
     )
 
+    kwargs_for_client = {}
+    kwargs_for_client['vertexai'] = self._isvertexai
+    if self._isvertexai:
+      kwargs_for_client['project'] = self._project
+      kwargs_for_client['location'] = self._location
+
     return Client(
-        vertexai=self._isvertexai,
         http_options=http_options,
+        **kwargs_for_client,
     )
 
   @override
diff --git a/tests/unittests/models/test_apigee_llm.py b/tests/unittests/models/test_apigee_llm.py
index eeafd5be..73005001 100644
--- a/tests/unittests/models/test_apigee_llm.py
+++ b/tests/unittests/models/test_apigee_llm.py
@@ -286,6 +286,42 @@ async def test_proxy_url_from_env_variable(mock_client_constructor):
     assert kwargs['http_options'].base_url == 'https://env.proxy.url'
 
 
+@pytest.mark.parametrize(
+    ('model_string', 'env_vars'),
+    [
+        (
+            'apigee/vertex_ai/gemini-2.5-flash',
+            {'GOOGLE_CLOUD_LOCATION': 'test-location'},
+        ),
+        (
+            'apigee/vertex_ai/gemini-2.5-flash',
+            {'GOOGLE_CLOUD_PROJECT': 'test-project'},
+        ),
+        (
+            'apigee/gemini-2.5-flash',
+            {
+                'GOOGLE_GENAI_USE_VERTEXAI': 'true',
+                'GOOGLE_CLOUD_LOCATION': 'test-location',
+            },
+        ),
+        (
+            'apigee/gemini-2.5-flash',
+            {
+                'GOOGLE_GENAI_USE_VERTEXAI': 'true',
+                'GOOGLE_CLOUD_PROJECT': 'test-project',
+            },
+        ),
+    ],
+)
+def test_vertex_model_missing_project_or_location_raises_error(
+    model_string, env_vars
+):
+  """Tests that ValueError is raised for Vertex models if project or location is missing."""
+  with mock.patch.dict(os.environ, env_vars, clear=True):
+    with pytest.raises(ValueError, match='environment variable must be set'):
+      ApigeeLlm(model=model_string, proxy_url=PROXY_URL)
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     (
@@ -359,6 +395,10 @@ async def test_model_string_parsing_and_client_initialization(
   if use_vertexai_env is not None:
     env_vars['GOOGLE_GENAI_USE_VERTEXAI'] = use_vertexai_env
 
+  if expected_is_vertexai:
+    env_vars['GOOGLE_CLOUD_PROJECT'] = 'test-project'
+    env_vars['GOOGLE_CLOUD_LOCATION'] = 'test-location'
+
   # The ApigeeLlm is initialized in the 'with' block to make sure that the mock
   # of the environment variable is active.
   with mock.patch.dict(os.environ, env_vars, clear=True):
@@ -382,6 +422,9 @@ async def test_model_string_parsing_and_client_initialization(
     mock_client_constructor.assert_called_once()
     _, kwargs = mock_client_constructor.call_args
     assert kwargs['vertexai'] == expected_is_vertexai
+    if expected_is_vertexai:
+      assert kwargs['project'] == 'test-project'
+      assert kwargs['location'] == 'test-location'
     http_options = kwargs['http_options']
     assert http_options.api_version == expected_api_version