How to uninstall Avast from a Mac - Setapp To start Avast uninstall on Mac, click on the Avast icon in your menu bar to open the app. Select Open Avast Security: When the app window appears on your screen, find Avast Security on the left side of your menu bar and click on it: Find Uninstall Avast Security option and click on that. This is the first step to remove Avast from your Mac.