--- qtbase/src/plugins/platforms/windows/qwindowscontext.cpp
+++ qtbase/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -1360,11 +1360,24 @@
     case QtWindows::MouseEvent:
     case QtWindows::LeaveEvent:
         {
-            QWindow *window = platformWindow->window();
+            QWindow *const platform_win = platformWindow->window();
+            QWindow *window = platform_win;
             while (window && (window->flags() & Qt::WindowTransparentForInput))
                 window = window->parent();
             if (!window)
                 return false;
+            if (window != platform_win) {
+                // In the case that a message is being redirected up to the parent window, remap
+                // msg.lParam (window coordinates) and msg.hwnd to refer to that parent window.
+                msg.hwnd = QWindowsBaseWindow::handleOf(window);
+                // Mouse wheel and non-client events have screen coordinates in msg.lParam and so
+                // don't need to be remapped.
+                if ((et != QtWindows::MouseWheelEvent) && !(et & QtWindows::NonClientEventFlag)) {
+                    POINT new_pos = { msg.pt.x, msg.pt.y };
+                    screenToClient(msg.hwnd, &new_pos);
+                    msg.lParam = MAKELPARAM(static_cast<unsigned short>(new_pos.x), static_cast<unsigned short>(new_pos.y));
+                }
+            }
             if (d->m_systemInfo & QWindowsContext::SI_SupportsPointer)
                 return sessionManagerInteractionBlocked() || d->m_pointerHandler.translateMouseEvent(window, hwnd, et, msg, result);
             else
--- qtbase/src/plugins/platforms/windows/qwindowsmousehandler.cpp
+++ qtbase/src/plugins/platforms/windows/qwindowsmousehandler.cpp
@@ -268,9 +268,9 @@
         return translateMouseWheelEvent(window, hwnd, msg, result);
 
     QPoint winEventPosition(GET_X_LPARAM(msg.lParam), GET_Y_LPARAM(msg.lParam));
-    if ((et & QtWindows::NonClientEventFlag) == 0 && QWindowsBaseWindow::isRtlLayout(hwnd))  {
+    if ((et & QtWindows::NonClientEventFlag) == 0 && QWindowsBaseWindow::isRtlLayout(msg.hwnd))  {
         RECT clientArea;
-        GetClientRect(hwnd, &clientArea);
+        GetClientRect(msg.hwnd, &clientArea);
         winEventPosition.setX(clientArea.right - winEventPosition.x());
     }
 
@@ -278,10 +278,10 @@
     QPoint globalPosition;
     if (et & QtWindows::NonClientEventFlag) {
         globalPosition = winEventPosition;
-        clientPosition = QWindowsGeometryHint::mapFromGlobal(hwnd, globalPosition);
+        clientPosition = QWindowsGeometryHint::mapFromGlobal(msg.hwnd, globalPosition);
     } else {
         clientPosition = winEventPosition;
-        globalPosition = QWindowsGeometryHint::mapToGlobal(hwnd, winEventPosition);
+        globalPosition = QWindowsGeometryHint::mapToGlobal(msg.hwnd, winEventPosition);
     }
 
     // Windows sends a mouse move with no buttons pressed to signal "Enter"
--- qtbase/src/plugins/platforms/windows/qwindowspointerhandler.cpp
+++ qtbase/src/plugins/platforms/windows/qwindowspointerhandler.cpp
@@ -699,9 +699,9 @@
     *result = 0;
 
     QPoint eventPos(GET_X_LPARAM(msg.lParam), GET_Y_LPARAM(msg.lParam));
-    if ((et & QtWindows::NonClientEventFlag) == 0 && QWindowsBaseWindow::isRtlLayout(hwnd))  {
+    if ((et & QtWindows::NonClientEventFlag) == 0 && QWindowsBaseWindow::isRtlLayout(msg.hwnd))  {
         RECT clientArea;
-        GetClientRect(hwnd, &clientArea);
+        GetClientRect(msg.hwnd, &clientArea);
         eventPos.setX(clientArea.right - eventPos.x());
     }
 
@@ -710,10 +710,10 @@
 
     if ((et == QtWindows::MouseWheelEvent) || (et & QtWindows::NonClientEventFlag)) {
         globalPos = eventPos;
-        localPos = QWindowsGeometryHint::mapFromGlobal(hwnd, eventPos);
+        localPos = QWindowsGeometryHint::mapFromGlobal(msg.hwnd, eventPos);
     } else {
         localPos = eventPos;
-        globalPos = QWindowsGeometryHint::mapToGlobal(hwnd, eventPos);
+        globalPos = QWindowsGeometryHint::mapToGlobal(msg.hwnd, eventPos);
     }
 
     const Qt::KeyboardModifiers keyModifiers = QWindowsKeyMapper::queryKeyboardModifiers();