diff --git a/ui/ozone/platform/x11/x11_window.cc b/ui/ozone/platform/x11/x11_window.cc
index b4c92dd8f3b15..85d8172299c08 100644
--- a/ui/ozone/platform/x11/x11_window.cc
+++ b/ui/ozone/platform/x11/x11_window.cc
@@ -1381,8 +1381,14 @@ void X11Window::DispatchUiEvent(ui::Event* event, const x11::Event& xev) {
   auto* window_manager = X11WindowManager::GetInstance();
   DCHECK(window_manager);
 
-  // Process X11-specific bits
+  // Process X11-specific bits. HandleEvent → OnCrossingEvent/OnFocusEvent →
+  // OnActivationChanged can synchronously close the widget and destroy |this|
+  // (see DesktopWindowTreeHostPlatform::OnActivationChanged).
+  auto weak_this = weak_ptr_factory_.GetWeakPtr();
   HandleEvent(xev);
+  if (!weak_this) {
+    return;
+  }
 
   x11::Event last_xev;
   std::unique_ptr<ui::Event> last_motion;