diff --git a/langserve/api_handler.py b/langserve/api_handler.py
index 4be0776e..0094d3e6 100644
--- a/langserve/api_handler.py
+++ b/langserve/api_handler.py
@@ -1565,11 +1565,27 @@ async def playground(
                 self._run_name, user_provided_config, request
             )
 
+        # Fetching the playground URL using information in the route
+        # to support a case when the APIRouter is nested inside another
+        # APIRouter.
+        # In this case the prefix attribute of the APIRouter is not enough
+        # to get the correct playground URL.
+        route = request.scope["route"]
+        suffix = "/{file_path:path}"
+        route_path = route.path
+        full_suffix = "/playground" + suffix
+
+        if not route_path.endswith(full_suffix):
+            raise AssertionError(
+                f"Expected route to end with " f"'{full_suffix}'. Got: {route.path}"
+            )
+
+        # path without the suffix
         playground_url = (
             request.scope.get("root_path", "").rstrip("/")
-            + self._base_url
-            + "/playground"
+            + route_path[: -len(f"{suffix}")]
         )
+
         feedback_enabled = tracing_is_enabled() and self._enable_feedback_endpoint
         public_trace_link_enabled = (
             tracing_is_enabled() and self._enable_public_trace_link_endpoint
diff --git a/tests/unit_tests/test_api_playground.py b/tests/unit_tests/test_api_playground.py
index 347aa63f..9caa8745 100644
--- a/tests/unit_tests/test_api_playground.py
+++ b/tests/unit_tests/test_api_playground.py
@@ -45,6 +45,10 @@ async def test_serve_playground_with_api_router() -> None:
     async with AsyncClient(app=app, base_url="http://localhost:9999") as client:
         response = await client.get("/langserve_runnables/chat/playground/index.html")
         assert response.status_code == 200
+        assert (
+            'src="/langserve_runnables/chat/playground/assets/'
+            in response.content.decode()
+        ), "html should contain reference to valid playground assets path"
 
 
 async def test_serve_playground_with_api_router_in_api_router() -> None:
@@ -67,6 +71,9 @@ async def test_serve_playground_with_api_router_in_api_router() -> None:
     async with AsyncClient(app=app, base_url="http://localhost:9999") as client:
         response = await client.get("/parent/bar/foo/playground/index.html")
         assert response.status_code == 200
+        assert (
+            'src="/parent/bar/foo/playground/assets/' in response.content.decode()
+        ), "html should contain reference to valid playground assets path"
 
 
 async def test_root_path_on_playground() -> None: