diff --git a/packages/react-native/React/CoreModules/RCTAlertController.mm b/packages/react-native/React/CoreModules/RCTAlertController.mm
index b275ebc5c67e..e8b13f071798 100644
--- a/packages/react-native/React/CoreModules/RCTAlertController.mm
+++ b/packages/react-native/React/CoreModules/RCTAlertController.mm
@@ -23,6 +23,7 @@ - (UIWindow *)alertWindow
     UIWindowScene *scene = RCTKeyWindow().windowScene;
     if (scene != nil) {
       _alertWindow = [[UIWindow alloc] initWithWindowScene:scene];
+      _alertWindow.frame = scene.coordinateSpace.bounds;
     } else {
       _alertWindow = [[UIWindow alloc] initWithFrame:UIScreen.mainScreen.bounds];
     }
diff --git a/packages/react-native/ReactCommon/react/renderer/components/modal/ModalHostViewUtils.mm b/packages/react-native/ReactCommon/react/renderer/components/modal/ModalHostViewUtils.mm
index 84be3c36c3d9..ef7e3a2b1894 100644
--- a/packages/react-native/ReactCommon/react/renderer/components/modal/ModalHostViewUtils.mm
+++ b/packages/react-native/ReactCommon/react/renderer/components/modal/ModalHostViewUtils.mm
@@ -13,8 +13,16 @@
 
 Size ModalHostViewScreenSize(void)
 {
-  CGSize screenSize = RCTScreenSize();
-  return {.width = screenSize.width, .height = screenSize.height};
+  __block CGSize viewportSize;
+
+  RCTUnsafeExecuteOnMainQueueSync(^{
+    viewportSize = RCTViewportSize();
+  });
+
+  return {
+    .width = viewportSize.width,
+    .height = viewportSize.height,
+  };
 }
 
 } // namespace facebook::react