Fletcher came through the ranks of Manchester United's Youth Academy and spent 20 years with United, making 342 appearances for the club. With them, he won five Premier Leagues, one FA Cup, two League Cups, the UEFA Champions League, four FA Community Shields and the FIFA Club World Cup. Fletcher was included in the PFA Premier League Team of the Year for 2009–10. He was named vice-captain in his last season with the club. He joined West Bromwich Albion in February 2015, where he made 97 appearances. After leaving Albion in 2017, Fletcher had a two-year stint with Stoke City. He returned to Manchester United in a coaching capacity in October 2020, working with the club's under-16s players, before being appointed to the first team in January 2021.