diff --git a/fastapi/routing.py b/fastapi/routing.py
index 9be2b44bc..3ac99a9c1 100644
--- a/fastapi/routing.py
+++ b/fastapi/routing.py
@@ -435,6 +435,31 @@ def get_request_handler(
             if isinstance(raw_response, Response):
                 if raw_response.background is None:
                     raw_response.background = solved_result.background_tasks
+                elif solved_result.background_tasks:
+                    from starlette.background import BackgroundTask, BackgroundTasks
+
+                    # Create a new BackgroundTasks to hold both
+                    combined_tasks = BackgroundTasks()
+
+                    # Add existing response tasks
+                    if isinstance(raw_response.background, BackgroundTasks):
+                        combined_tasks.tasks.extend(raw_response.background.tasks)
+                    elif isinstance(raw_response.background, BackgroundTask):
+                        combined_tasks.tasks.append(raw_response.background)
+
+                    # Add dependency tasks
+                    # solved_result.background_tasks is always BackgroundTasks (from dependencies/utils.py)
+                    if isinstance(solved_result.background_tasks, BackgroundTasks):
+                        combined_tasks.tasks.extend(
+                            solved_result.background_tasks.tasks
+                        )
+                    elif isinstance(
+                        solved_result.background_tasks, BackgroundTask
+                    ):  # pragma: no cover
+                        # Should not happen for BackgroundTasks dependency but safe to handle
+                        combined_tasks.tasks.append(solved_result.background_tasks)
+
+                    raw_response.background = combined_tasks
                 response = raw_response
             else:
                 response_args: Dict[str, Any] = {
diff --git a/tests/test_issue_11215.py b/tests/test_issue_11215.py
new file mode 100644
index 000000000..00e4cfa82
--- /dev/null
+++ b/tests/test_issue_11215.py
@@ -0,0 +1,24 @@
+from fastapi import BackgroundTasks, FastAPI
+from fastapi.testclient import TestClient
+from starlette.responses import BackgroundTask, Response
+
+app = FastAPI()
+
+
+@app.get("/")
+def endpoint(tasks: BackgroundTasks):
+    tasks.add_task(lambda: print("Dependency task executed"))
+    return Response(
+        content="Custom response",
+        background=BackgroundTask(lambda: print("Response task executed")),
+    )
+
+
+client = TestClient(app)
+
+
+def test_issue_11215(capsys):
+    client.get("/")
+    captured = capsys.readouterr()
+    assert "Dependency task executed" in captured.out
+    assert "Response task executed" in captured.out
diff --git a/tests/test_issue_11215_coverage.py b/tests/test_issue_11215_coverage.py
new file mode 100644
index 000000000..1eaa96fc5
--- /dev/null
+++ b/tests/test_issue_11215_coverage.py
@@ -0,0 +1,29 @@
+from fastapi import BackgroundTasks, FastAPI
+from fastapi.testclient import TestClient
+from starlette.background import BackgroundTasks as StarletteBackgroundTasks
+from starlette.responses import Response
+
+app = FastAPI()
+
+
+@app.get("/")
+def endpoint(tasks: BackgroundTasks):
+    tasks.add_task(lambda: print("Dependency task"))
+
+    response_tasks = StarletteBackgroundTasks()
+    response_tasks.add_task(lambda: print("Response task"))
+
+    return Response(
+        content="Custom response",
+        background=response_tasks,
+    )
+
+
+client = TestClient(app)
+
+
+def test_issue_11215_response_background_tasks_collection(capsys):
+    client.get("/")
+    captured = capsys.readouterr()
+    assert "Dependency task" in captured.out
+    assert "Response task" in captured.out