The application closes when you click on the top right X of the top window(the one called in main function) inside the app, or the X in task manager, or when you call the function qApp->exit() (which is the inherited QCoreApplication::exit() you wrote; qApp is a global pointer to your QApplication istance) . When the app closes, the event loop handles all closing events, so you can put the kill all execution inside the main window destructor, MainWindow::~MainWindow() usually with QtCreator, to make it launch when the app is closing.