Butt, who was part of the legendary 'Class of '92' at Old Trafford, will assist interim manager Ryan Giggs in the club's final four games of the season.
Moyes was sacked on Tuesday after witnessing his side lose 15 games in all competitions, as well as failing to qualify for the Champions League.
"It will be massive for us, a proud moment for us all," Butt told MUTV. "To be there together is a bit of a surreal thing. We walked in here together when we were 12 and to be here now - I'm not 40 yet but Giggsy is, and myself and Scholes are nearly there too. So for us and Phil to be there together is a very proud moment.
"We're here to try to help the club and get the results that we want from now until the end of the season. What happens after that, who knows?"
United's first game with the new coaching team will be at home to Norwich City on Saturday.