The fight between O'Malley and Almeida ended in the third round.
The American sent his opponent to the canvas with a left straight, and then finished off on the ground.
O'Malley won his 13th career win and closed the defeat to Marlon Vera.
Almeida suffered a fifth defeat.
Earlier it was reported that ex-lightweight champion Khabib Nurmagomedov received an award from the creators of the UFC 4 game.