Fletcher returned to United in 2021, having previously spent 20 years at the club as a player, making over 340 appearances.
After graduating from the Academy, Fletcher won five Premier League titles, two League Cups, the FA Cup, the Champions League and the FIFA Club World Cup.
Fletcher has started his new role with immediate effect, taking charge of the group’s pre-season preparations which began with a training camp at the adidas global headquarters in Herzogenaurach, Germany, and a game against Queens Park Rangers in a friendly at Carrington.
Darren Fletcher said: “I am really excited to take on this new role and increase my responsibility to directly develop our young players.