The 19-year-old forward, who turns 20 later this month, joins Gary Caldwell’s side for the 2026-27 League One campaign after gaining valuable experience on loan at German club FC Nurnberg and Championship side West Bromwich Albion last season.
A Crystal Palace academy product since the age of nine, Mustapha has progressed through every youth level at Selhurst Park.
He enjoyed an outstanding spell with the club’s academy teams, registering 16 goals and 17 assists in 57 appearances across the Under-18 Premier League and Premier League 2 before establishing himself with the Under-21s.
“I am more than happy - I am really excited to get going and show what I can do in a Wigan Athletic shirt,” Mustapha told club website.
“It’s a big Football Club, and I believe I can come here and really kick on.
“The Gaffer seems very genuine, and his vision really excites me. I am really looking forward to working with him.
“On the ball, I like to make things happen. I want to excite fans and get bums off seats.”