Former Aberdeen manager Sir Alex Ferguson included Ryan Giggs, Paul Scholes and Rio Ferdinand in a star-studded side as he returned to the Granite City for the match in honour of his former player, who is currently the head of the Pittodrie youth academy.
Fletcher, who is on the road to recovery from a chronic inflammatory bowel condition, featured for United for the first time since a Champions League match against Benfica last November, coming on a second-half substitute.
Former Old Trafford favourites Dwight Yorke, Clayton Blackmore and Quinton Fortune all made cameo appearances, while the home support were also treated to a trip down memory lane with Brian Irvine, Dougie Bell, Doug Rougvie and Steve Tosh all donning an Aberdeen top once again.
The hosts took an unexpected lead after 38 minutes when Jonny Hayes pounced on a rare lapse by Scholes when he dispossessed the midfielder and coolly slotted the ball past David De Gea.
Fletcher was introduced just before the half-hour mark to a warm reception from the Pittodrie crowd before Aberdeen doubled their lead when Joe Shaughnessy turned the ball home from an Andrew Considine pass after United failed to deal with a Rob Milsom corner.
Yorke had a strike ruled out for offside before Anderson pulled a goal back for United after 81 minutes with a neat finish. But Aberdeen held on for a surprise victory against the English Premier League giants.
Ferguson told MUTV after the match: "It's been quiet progress for the boy.
"He joined in training a couple of weeks ago and it's one of those situations where you say: 'Let's see how he does because he has had a really difficult time in the last year'."
He went on: "Therefore, I wasn't really placing too much hope in it but let's see how he does.
"He's got to the stage now where he feels he needs a game. I let him join Scotland this week but he wanted a game so I said: 'Come to Aberdeen and join up afterwards'.
"I'll give him 20 to 25 minutes."