Can we see the code how you set modality ?
First of all, my dialog is a separate ui file, not a QDialog thing. So it's a new class called MessageDialogs. I sticked with this way instead of using QDialog for particular project reasons.

Anyway..What I did is - just creating an instance of the MessageDialogs( let's call it myMessageDialog) and typing myMessageDialog->setWindowModality(Qt::ApplicationModal);