The two remaining members of Migos performed the group's hit Bad and Boujee in an unannounced appearance.
It was the pair's first performance together since Takeoff was shot dead last November at the age of 28.
Also at Sunday's BET ceremony in Los Angeles, Beyoncé and SZA were joint winners of the award for best album and picked up two more prizes each.
In their tribute, Offest shouted "Doing this for Take!" while pointing at a screen showing a picture of a rocket, which morphed into a large image of their late bandmate.
