diff --git a/pydantic_settings/sources/providers/gcp.py b/pydantic_settings/sources/providers/gcp.py
index ba202222..62f356a7 100644
--- a/pydantic_settings/sources/providers/gcp.py
+++ b/pydantic_settings/sources/providers/gcp.py
@@ -37,10 +37,11 @@ class GoogleSecretManagerMapping(Mapping[str, Optional[str]]):
     _loaded_secrets: dict[str, str | None]
     _secret_client: SecretManagerServiceClient
 
-    def __init__(self, secret_client: SecretManagerServiceClient, project_id: str) -> None:
+    def __init__(self, secret_client: SecretManagerServiceClient, project_id: str, case_sensitive: bool) -> None:
         self._loaded_secrets = {}
         self._secret_client = secret_client
         self._project_id = project_id
+        self._case_sensitive = case_sensitive
 
     @property
     def _gcp_project_path(self) -> str:
@@ -48,15 +49,22 @@ def _gcp_project_path(self) -> str:
 
     @cached_property
     def _secret_names(self) -> list[str]:
-        return [
-            self._secret_client.parse_secret_path(secret.name).get('secret', '')
-            for secret in self._secret_client.list_secrets(parent=self._gcp_project_path)
-        ]
+        rv: list[str] = []
+
+        secrets = self._secret_client.list_secrets(parent=self._gcp_project_path)
+        for secret in secrets:
+            name = self._secret_client.parse_secret_path(secret.name).get('secret', '')
+            if not self._case_sensitive:
+                name = name.lower()
+            rv.append(name)
+        return rv
 
     def _secret_version_path(self, key: str, version: str = 'latest') -> str:
         return self._secret_client.secret_version_path(self._project_id, key, version)
 
     def __getitem__(self, key: str) -> str | None:
+        if not self._case_sensitive:
+            key = key.lower()
         if key not in self._loaded_secrets:
             # If we know the key isn't available in secret manager, raise a key error
             if key not in self._secret_names:
@@ -92,6 +100,7 @@ def __init__(
         env_parse_none_str: str | None = None,
         env_parse_enums: bool | None = None,
         secret_client: SecretManagerServiceClient | None = None,
+        case_sensitive: bool | None = True,
     ) -> None:
         # Import Google Packages if they haven't already been imported
         if SecretManagerServiceClient is None or Credentials is None or google_auth_default is None:
@@ -124,7 +133,7 @@ def __init__(
 
         super().__init__(
             settings_cls,
-            case_sensitive=True,
+            case_sensitive=case_sensitive,
             env_prefix=env_prefix,
             env_ignore_empty=False,
             env_parse_none_str=env_parse_none_str,
@@ -132,7 +141,9 @@ def __init__(
         )
 
     def _load_env_vars(self) -> Mapping[str, Optional[str]]:
-        return GoogleSecretManagerMapping(self._secret_client, project_id=self._project_id)
+        return GoogleSecretManagerMapping(
+            self._secret_client, project_id=self._project_id, case_sensitive=self.case_sensitive
+        )
 
     def __repr__(self) -> str:
         return f'{self.__class__.__name__}(project_id={self._project_id!r}, env_nested_delimiter={self.env_nested_delimiter!r})'
diff --git a/tests/test_source_gcp_secret_manager.py b/tests/test_source_gcp_secret_manager.py
index d5b13b1f..e43c45ad 100644
--- a/tests/test_source_gcp_secret_manager.py
+++ b/tests/test_source_gcp_secret_manager.py
@@ -57,7 +57,7 @@ def mock_access_secret_version(name: str):
 
 @pytest.fixture
 def secret_manager_mapping(mock_secret_client):
-    return GoogleSecretManagerMapping(mock_secret_client, 'test-project')
+    return GoogleSecretManagerMapping(mock_secret_client, project_id='test-project', case_sensitive=True)
 
 
 @pytest.fixture
@@ -96,6 +96,13 @@ def test_secret_manager_mapping_getitem_success(self, secret_manager_mapping):
         value = secret_manager_mapping['test-secret']
         assert value == 'test-value'
 
+    def test_secret_manager_mapping_getitem_case_insensitive_success(self, mock_secret_client):
+        case_insensitive_mapping = GoogleSecretManagerMapping(
+            mock_secret_client, project_id='test-project', case_sensitive=False
+        )
+        value = case_insensitive_mapping['TEST-SECRET']
+        assert value == 'test-value'
+
     def test_secret_manager_mapping_getitem_nonexistent_key(self, secret_manager_mapping):
         with pytest.raises(KeyError):
             _ = secret_manager_mapping['nonexistent-secret']