The 16-year-old, born in Germany on 26 January 1997 of Ethiopian descent, is in line for his debut against FA Cup opponents Tottenham today.
Zelalem was spotted by Arsenal scout and former Gunner Danny Karbassiyoon playing in the Dallas Cup, and impressed during the club's pre-season tour.
"I don't listen to any hype or anything like that," Zelalem had said. "I just listen to my parents and the people around me who love me. They keep me grounded, so it's fine.
"I have really high expectations for myself, so, hopefully, I might be able to make a few appearances this season.
"But I'm still very young, so I have a lot of work to do. I will keep working hard and stay positive all the time."