How to Change QMessageBox Icon and Title

However you can use of QMessageBox::critical(0, "Error", "An error has occured !"); because critical(...) method is static and theres no need for create an instance of QMessageBox.

Use bellow code :

QMessageBox mb("Application Name",
                           "Hardware failure.\n\nDisk error detected\nDo you want to stop?",
                           QMessageBox::NoIcon,
                           QMessageBox::Yes | QMessageBox::Default,
                           QMessageBox::NoButton,
                           QMessageBox::NoButton);

QPixmap exportSuccess("/media/msi/Information/Pictures/Icons/Icons Pack/PNG/48X48/about.png");
mb.setIconPixmap(exportSuccess);
mb.exec();

This example work 100%

Simply you can set Icon for your Application it will automatically set on your MessegeBox