The 37-year-old was drafted into Ole Gunnar Solskjaer’s coaching set-up in January after a spell coaching the club’s Under-16s, and is believed to have impressed Old Trafford chiefs laying plans to beef up the club’s football operations department.
Dalkeith-born Fletcher is United’s first ever technical director and will focus on a “co-ordinated and long-term approach to player and squad development”.
He will also be tasked with assisting newly-appointed football director John Murtough as well as “adding technical input and direction into all football and performance areas”.
United’s executive vice-chairman Ed Woodward said: "These are hugely important appointments that reinforce the progress we have been making as a club in recent years in our relentless pursuit of success.
"We have already made great strides forward in the way we run our football operations, and the benefits are visible in the resurgent pipeline of academy talent reaching the first team and through our improved recruitment record.
"John has been integral to our progress in these areas and his deep understanding of development ensures the club's traditions of bringing young players through from academy to first team will continue.
"Darren's stellar achievements as a player and his own journey from academy to Premier League and Champions League winner means he naturally commands respect and understands this vital part of the club's DNA.
"In this new role, the first in our history, he will deliver technical advice across all aspects of the football department as well as contributing to the communication and delivery of our football philosophy across all areas of the club.”
Fletcher added: “It is great to be back with the club and I am delighted to be taking on this new role. We are moving in the right direction and I am looking forward to continuing to work with Ole and his coaching team, and now with John as the football director, to help bring young players through and further develop the football side of the club.
"It's fantastic to see that all the staff here are driving Manchester United forward towards a new era of success."
Fletcher grew up in Mayfield and began his football career with Hutchison Vale, before spells as a youth with Tynecastle Boys Club and Celtic Boys Club saw him attract the attention of United scouts.
He joined the Old Trafford set-up at the age of 11, signing a professional deal four years later.
He made his debut in 2003 and went on to play more than 340 games for the Red Devils, winning five Premier League titles, one FA Cup, one League Cup, and the Champions League in 2008 among other honours.
He was capped 80 times by Scotland, scoring five goals, between 2003 and 2017 and often wore the captain’s armband.
Fletcher wound down his career with two-year spells at West Bromwich Albion and Stoke City. He said in May 2020 that he was unlikely to play football again as a result of his medical condition, ulcerative colitis, making him more susceptible to Covid-19.