@VRonin Thank you for your suggestion! Interestingly that doesn't have any effect. The application still uses the unified menubar. I set the attribute like this in my main() before I construct and show the QMainWindow: QCoreApplication::setAttribute(Qt::AA_DontUseNativeMenuBar, true); Interestingly I get the following debug messages in the application output pane when opening and closing the application when the attribute is set to true: Menu item is already in a menu, remove it from the other menu first before inserting Menu item is already in a menu, remove it from the other menu first before inserting Menu item is already in a menu, remove it from the other menu first before inserting Menu item is already in a menu, remove it from the other menu first before inserting Item to remove does not belong to this menu Item to remove does not belong to this menu Item to remove does not belong to this menu Item to remove does not belong to this menu I also tried QMainWindow::setUnifiedTitleAndToolBarOnMac() but without any success either. The application still uses the unified toolbar. I'm using Qt 5.6 on OS X 10.11.4 (El Capitan)