diff --git a/scene/main/viewport.cpp b/scene/main/viewport.cpp
index ddf9cac7dde..d2be1ce6a71 100644
--- a/scene/main/viewport.cpp
+++ b/scene/main/viewport.cpp
@@ -2663,6 +2663,11 @@ bool Viewport::_sub_windows_forward_input(const Ref<InputEvent> &p_event) {
 				} else {
 					gui.subwindow_resize_mode = _sub_window_get_resize_margin(sw.window, mb->get_position());
 					if (gui.subwindow_resize_mode != SUB_WINDOW_RESIZE_DISABLED) {
+						if (gui.subwindow_focused != sw.window) {
+							// Refocus.
+							_sub_window_grab_focus(sw.window);
+						}
+
 						gui.subwindow_resize_from_rect = r;
 						gui.subwindow_drag_from = mb->get_position();
 						gui.subwindow_drag = SUB_WINDOW_DRAG_RESIZE;