diff --git a/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py b/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
index 8ba83985c6..f9925349f9 100644
--- a/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
+++ b/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
@@ -190,7 +190,7 @@ def client_response_hook(span: Span, scope: dict[str, Any], message: dict[str, A
 import fastapi
 from starlette.applications import Starlette
 from starlette.middleware.errors import ServerErrorMiddleware
-from starlette.routing import Match
+from starlette.routing import Match, Route
 from starlette.types import ASGIApp
 
 from opentelemetry.instrumentation._semconv import (
@@ -448,7 +448,11 @@ def _get_route_details(scope):
     route = None
 
     for starlette_route in app.routes:
-        match, _ = starlette_route.matches(scope)
+        match, _ = (
+            Route.matches(starlette_route, scope)
+            if isinstance(starlette_route, Route)
+            else starlette_route.matches(scope)
+        )
         if match == Match.FULL:
             route = starlette_route.path
             break
diff --git a/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py b/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
index 523c165f85..8a107089c7 100644
--- a/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
+++ b/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
@@ -22,7 +22,10 @@
 import fastapi
 from fastapi.middleware.httpsredirect import HTTPSRedirectMiddleware
 from fastapi.responses import JSONResponse
+from fastapi.routing import APIRoute
 from fastapi.testclient import TestClient
+from starlette.routing import Match
+from starlette.types import Receive, Scope, Send
 
 import opentelemetry.instrumentation.fastapi as otel_fastapi
 from opentelemetry import trace
@@ -38,9 +41,7 @@
 from opentelemetry.instrumentation.auto_instrumentation._load import (
     _load_instrumentors,
 )
-from opentelemetry.instrumentation.dependencies import (
-    DependencyConflict,
-)
+from opentelemetry.instrumentation.dependencies import DependencyConflict
 from opentelemetry.sdk.metrics.export import (
     HistogramDataPoint,
     NumberDataPoint,
@@ -123,6 +124,23 @@
 )
 
 
+class CustomMiddleware:
+    def __init__(self, app: fastapi.FastAPI) -> None:
+        self.app = app
+
+    async def __call__(
+        self, scope: Scope, receive: Receive, send: Send
+    ) -> None:
+        scope["nonstandard_field"] = "here"
+        await self.app(scope, receive, send)
+
+
+class CustomRoute(APIRoute):
+    def matches(self, scope: Scope) -> tuple[Match, Scope]:
+        assert "nonstandard_field" in scope
+        return super().matches(scope)
+
+
 class TestBaseFastAPI(TestBase):
     def _create_app(self):
         app = self._create_fastapi_app()
@@ -183,6 +201,7 @@ def setUp(self):
         self._instrumentor = otel_fastapi.FastAPIInstrumentor()
         self._app = self._create_app()
         self._app.add_middleware(HTTPSRedirectMiddleware)
+        self._app.add_middleware(CustomMiddleware)
         self._client = TestClient(self._app, base_url="https://testserver:443")
         # run the lifespan, initialize the middleware stack
         # this is more in-line with what happens in a real application when the server starts up
@@ -202,6 +221,7 @@ def tearDown(self):
     def _create_fastapi_app():
         app = fastapi.FastAPI()
         sub_app = fastapi.FastAPI()
+        custom_router = fastapi.APIRouter(route_class=CustomRoute)
 
         @sub_app.get("/home")
         async def _():
@@ -227,6 +247,12 @@ async def _():
         async def _():
             raise UnhandledException("This is an unhandled exception")
 
+        @custom_router.get("/success")
+        async def _():
+            return None
+
+        app.include_router(custom_router, prefix="/custom-router")
+
         app.mount("/sub", app=sub_app)
 
         return app
@@ -304,6 +330,14 @@ def test_sub_app_fastapi_call(self):
             span.attributes[HTTP_URL],
         )
 
+    def test_custom_api_router(self):
+        """
+        This test is to ensure that custom API routers the OpenTelemetryMiddleware does not cause issues with
+        custom API routers that depend on non-standard fields on the ASGI scope.
+        """
+        resp = self._client.get("/custom-router/success")
+        self.assertEqual(resp.status_code, 200)
+
 
 class TestBaseAutoFastAPI(TestBaseFastAPI):
     @classmethod
@@ -988,6 +1022,7 @@ def test_metric_uninstrument(self):
     def _create_fastapi_app():
         app = fastapi.FastAPI()
         sub_app = fastapi.FastAPI()
+        custom_router = fastapi.APIRouter(route_class=CustomRoute)
 
         @sub_app.get("/home")
         async def _():
@@ -1013,6 +1048,12 @@ async def _():
         async def _():
             raise UnhandledException("This is an unhandled exception")
 
+        @custom_router.get("/success")
+        async def _():
+            return None
+
+        app.include_router(custom_router, prefix="/custom-router")
+
         app.mount("/sub", app=sub_app)
 
         return app