diff --git a/libs/WindowManager/Shell/res/values/strings.xml b/libs/WindowManager/Shell/res/values/strings.xml
index 9fab3a1eb4b94..25eddf834f3da 100644
--- a/libs/WindowManager/Shell/res/values/strings.xml
+++ b/libs/WindowManager/Shell/res/values/strings.xml
@@ -66,8 +66,10 @@
     <!-- Multi-Window strings -->
     <!-- Text that gets shown on top of current activity to inform the user that the system force-resized the current activity to be displayed in split-screen and that things might crash/not work properly [CHAR LIMIT=NONE] -->
     <string name="dock_forced_resizable">App may not work with split-screen.</string>
-    <!-- Warning message when we try to dock a non-resizeable task and launch it in fullscreen instead. -->
+    <!-- Warning message when we try to dock a non-resizeable task and launch it in fullscreen instead  [CHAR LIMIT=NONE] -->
     <string name="dock_non_resizeble_failed_to_dock_text">App does not support split-screen.</string>
+    <!-- Warning message when we try to dock an app not supporting multiple instances split into multiple sides [CHAR LIMIT=NONE] -->
+    <string name="dock_multi_instances_not_supported_text">This app can only be opened in 1 window.</string>
     <!-- Text that gets shown on top of current activity to inform the user that the system force-resized the current activity to be displayed on a secondary display and that things might crash/not work properly [CHAR LIMIT=NONE] -->
     <string name="forced_resizable_secondary_display">App may not work on a secondary display.</string>
     <!-- Warning message when we try to launch a non-resizeable activity on a secondary display and launch it on the primary instead. -->
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java
index 1774dd5e3b6f1..a79ac45228cad 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java
@@ -58,6 +58,7 @@ import android.view.RemoteAnimationTarget;
 import android.view.SurfaceControl;
 import android.view.SurfaceSession;
 import android.view.WindowManager;
+import android.widget.Toast;
 import android.window.RemoteTransition;
 import android.window.WindowContainerTransaction;
 
@@ -597,6 +598,10 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
             } else if (isSplitScreenVisible()) {
                 mStageCoordinator.switchSplitPosition("startIntent");
                 return;
+            } else {
+                Toast.makeText(mContext, R.string.dock_multi_instances_not_supported_text,
+                        Toast.LENGTH_SHORT).show();
+                return;
             }
         }