modelcontextprotocol
diff --git a/src/mcp/client/auth/oauth2.py b/src/mcp/client/auth/oauth2.py
@@ -464,6 +464,10 @@ async def _initialize(self) -> None:  # pragma: no cover
         """Load stored tokens and client info."""
         self.context.current_tokens = await self.context.storage.get_tokens()
         self.context.client_info = await self.context.storage.get_client_info()
+
+        if self.context.current_tokens and self.context.current_tokens.expires_in is not None:
+            self.context.update_token_expiry(self.context.current_tokens)
+
         self._initialized = True
 
     def _add_auth_header(self, request: httpx.Request) -> None:

diff --git a/tests/client/test_auth.py b/tests/client/test_auth.py
@@ -82,6 +82,17 @@ def valid_tokens():
     )
 
 
+@pytest.fixture
+def expired_tokens():
+    return OAuthToken(
+        access_token="test_access_token",
+        token_type="Bearer",
+        expires_in=-100,  # Expired 100 seconds ago
+        refresh_token="test_refresh_token",
+        scope="read write",
+    )
+
+
 @pytest.fixture
 def oauth_provider(client_metadata: OAuthClientMetadata, mock_storage: MockTokenStorage):
     async def redirect_handler(url: str) -> None:
@@ -259,6 +270,100 @@ def test_clear_tokens(self, oauth_provider: OAuthClientProvider, valid_tokens: O
         assert context.token_expiry_time is None
 
 
+class TestTokenInitialization:
+    """Test token loading from storage during initialization."""
+
+    @pytest.mark.anyio
+    async def test_initialize_sets_token_expiry_from_stored_tokens(
+        self, oauth_provider: OAuthClientProvider, valid_tokens: OAuthToken
+    ):
+        """Test _initialize() sets token_expiry_time when loading tokens from storage."""
+        context = oauth_provider.context
+        await context.storage.set_tokens(valid_tokens)
+
+        # Before initialization
+        assert oauth_provider._initialized is False
+        assert context.current_tokens is None
+        assert context.token_expiry_time is None
+
+        # Trigger initialization by starting auth flow
+        test_request = httpx.Request("GET", "https://api.example.com/v1/mcp")
+        auth_flow = oauth_provider.async_auth_flow(test_request)
+
+        # First request calls _initialize()
+        request = await auth_flow.__anext__()
+
+        # After first request, verify tokens were loaded
+        assert oauth_provider._initialized is True
+        assert oauth_provider.context.current_tokens is not None
+        assert oauth_provider.context.current_tokens.access_token == "test_access_token"
+
+        # token_expiry_time should be set by update_token_expiry()
+        assert oauth_provider.context.token_expiry_time is not None
+
+        # Verify token is considered valid
+        assert oauth_provider.context.is_token_valid() is True
+
+        # Request should have auth header added
+        assert request.headers["Authorization"] == "Bearer test_access_token"
+
+        # Complete the flow
+        response = httpx.Response(200, request=request)
+        try:
+            await auth_flow.asend(response)
+        except StopAsyncIteration:
+            pass
+
+    @pytest.mark.anyio
+    async def test_initialize_with_expired_tokens_detects_expiry(
+        self, oauth_provider: OAuthClientProvider, expired_tokens: OAuthToken
+    ):
+        """Test that expired tokens loaded from storage are detected as invalid."""
+        context = oauth_provider.context
+        await context.storage.set_tokens(expired_tokens)
+        await context.storage.set_client_info(
+            OAuthClientInformationFull(
+                client_id="test_client_id",
+                client_secret="test_client_secret",
+                redirect_uris=[AnyUrl("http://localhost:3030/callback")],
+            )
+        )
+
+        # First request
+        test_request = httpx.Request("GET", "https://api.example.com/v1/mcp")
+        auth_flow = oauth_provider.async_auth_flow(test_request)
+
+        # This should trigger a refresh attempt, not the original request
+        refresh_request = await auth_flow.__anext__()
+
+        # Verify tokens were loaded
+        assert context.current_tokens is not None
+
+        # token_expiry_time should be set by update_token_expiry()
+        assert context.token_expiry_time is not None
+
+        # Token should be detected as invalid (expired)
+        assert context.is_token_valid() is False
+
+        # Should be able to refresh
+        assert context.can_refresh_token() is True
+
+        # Complete the flow
+        refresh_response = httpx.Response(
+            200,
+            content=b'{"access_token": "new_token", "token_type": "Bearer", "expires_in": 3600}',
+            request=refresh_request,
+        )
+        try:
+            original_request = await auth_flow.asend(refresh_response)
+            # Should retry original request with new token
+            assert original_request.headers["Authorization"] == "Bearer new_token"
+            final_response = httpx.Response(200, request=original_request)
+            await auth_flow.asend(final_response)
+        except StopAsyncIteration:
+            pass
+
+
 class TestOAuthFlow:
     """Test OAuth flow methods."""