diff --git a/src/agents/mcp/manager.py b/src/agents/mcp/manager.py
index 94df096d04..733e744363 100644
--- a/src/agents/mcp/manager.py
+++ b/src/agents/mcp/manager.py
@@ -200,7 +200,7 @@ def __init__(
         suppress_cancelled_error: bool = True,
         connect_in_parallel: bool = False,
     ) -> None:
-        self._all_servers = list(servers)
+        self._all_servers = self._unique_servers(servers)
         self._active_servers = list(self._all_servers)
         self.connect_timeout_seconds = connect_timeout_seconds
         self.cleanup_timeout_seconds = cleanup_timeout_seconds
diff --git a/tests/mcp/test_mcp_server_manager_cleanup_state.py b/tests/mcp/test_mcp_server_manager_cleanup_state.py
index bf6c82ef65..f411f464d8 100644
--- a/tests/mcp/test_mcp_server_manager_cleanup_state.py
+++ b/tests/mcp/test_mcp_server_manager_cleanup_state.py
@@ -29,6 +29,22 @@ async def test_cleanup_all_removes_cleaned_servers_from_active_servers() -> None
     assert server.connect.await_count == 2
 
 
+@pytest.mark.asyncio
+async def test_manager_owns_repeated_server_instance_once() -> None:
+    server = cast(MCPServer, Mock(spec=MCPServer))
+    server.connect = AsyncMock()
+    server.cleanup = AsyncMock()
+
+    manager = MCPServerManager([server, server])
+
+    assert manager.all_servers == [server]
+    assert await manager.connect_all() == [server]
+    await manager.cleanup_all()
+
+    server.connect.assert_awaited_once()
+    server.cleanup.assert_awaited_once()
+
+
 @pytest.mark.asyncio
 async def test_cleanup_all_refreshes_active_servers_when_cancellation_propagates() -> None:
     server = cast(MCPServer, Mock(spec=MCPServer))