Teams pop-up notifications can be controlled through the Settings screen:

  1. Click on your initials/photo at the top right, then Settings:
  2. Click on Notifications:


  3. For each of the entries (Chat/Meetings/People/Other) you can click Edit and pick which notifications you want - where it is set to "Banner" it will pop up, "Feed" it shouldn't pop up.
  4. Finally you can click on Custom and there are some more settings which can be turned off.
  5. As a final step you can turn off notifications completely within Windows by clicking the Start menu then begin typing in "Notifications", then click on Notifications and actions settings when it appears:
  6. You can then turn off notifications altogether here: