The 21-year-old spent last season on loan at La Liga side Granada, scoring five goals in 37 appearances across all competitions during his time in Spain.
Pereira was unable to prevent Granada from suffering relegation from La Liga, but having returned to Old Trafford he is now hopeful of playing his way into Jose Mourinho's plans.
"I am very happy that I am back, and I can be part of this team," he told MUTV.
"I will try to do my best to stay here, get an important role for the season, to help my teammates and to impress the manager.
"It boosts me that the people here trust the young players. I am very happy for the young players and I want to be a part of this team as well."
Pereira, who has only made 13 senior appearances for United before, is currently with the squad on their pre-season tour of the United States.