diff --git a/lcl/interfaces/qt/qtwidgets.pas b/lcl/interfaces/qt/qtwidgets.pas
index 75a1a9046d..5712eb86f5 100644
--- a/lcl/interfaces/qt/qtwidgets.pas
+++ b/lcl/interfaces/qt/qtwidgets.pas
@@ -3970,14 +3970,19 @@ begin
   LastMouse.WinControl := LCLObject;
   LastMouse.WinHandle := TLCLIntfHandle(Self);
   LastMouse.MousePos := Point(MousePos.X, MousePos.Y);
-  
-  Msg.Msg := LM_MOUSEWHEEL;
 
   Msg.X := SmallInt(MousePos.X);
   Msg.Y := SmallInt(MousePos.Y);
 
   Msg.WheelDelta := SmallInt(QWheelEvent_delta(QWheelEventH(Event)));
 
+  Msg.Msg := LM_MOUSEWHEEL;
+  if QWheelEvent_orientation(QWheelEventH(Event)) = QtHorizontal then
+  begin
+    Msg.Msg := LM_MOUSEHWHEEL;
+    Msg.WheelDelta := -Msg.WheelDelta;
+  end;
+
   {$IFDEF DARWIN}
   // LCL expects delta +-120, we must fix it. issue #20888
   if (ChildOfComplexWidget in [ccwCustomControl, ccwAbstractScrollArea,
diff --git a/lcl/interfaces/qt5/qtwidgets.pas b/lcl/interfaces/qt5/qtwidgets.pas
index 87e76ab0ea..5476799579 100644
--- a/lcl/interfaces/qt5/qtwidgets.pas
+++ b/lcl/interfaces/qt5/qtwidgets.pas
@@ -3892,14 +3892,19 @@ begin
   LastMouse.WinControl := LCLObject;
   LastMouse.WinHandle := TLCLIntfHandle(Self);
   LastMouse.MousePos := Point(MousePos.X, MousePos.Y);
-  
-  Msg.Msg := LM_MOUSEWHEEL;
 
   Msg.X := SmallInt(MousePos.X);
   Msg.Y := SmallInt(MousePos.Y);
 
   Msg.WheelDelta := SmallInt(QWheelEvent_delta(QWheelEventH(Event)));
 
+  Msg.Msg := LM_MOUSEWHEEL;
+  if QWheelEvent_orientation(QWheelEventH(Event)) = QtHorizontal then
+  begin
+    Msg.Msg := LM_MOUSEHWHEEL;
+    Msg.WheelDelta := -Msg.WheelDelta;
+  end;
+
   {$IFDEF DARWIN}
   // LCL expects delta +-120, we must fix it. issue #20888
   if (ChildOfComplexWidget in [ccwCustomControl, ccwAbstractScrollArea,