The 36-year-old had been expected to be appointed within the new-look staff at Old Trafford following his arrival at Carrington training ground this morning.
Neville initially planned to prolong his playing career following his decision to leave Everton, but eventually opted to retire from the game and join up with his former boss at the Premier League-winning outfit.
"I have known and worked with Philip for eight years and in that time I have come to know his dedication, ability to lead and appetite for hard work," said Moyes. "In addition, of course, he understands the club very well and I think his addition to the coaching staff will be a valuable one."
Neville added: "When I retired from football I knew that I wanted to continue in the game - it's something I've been preparing for over the last few years, so when David called to give me this opportunity, I couldn't resist. I gave my all when I played for Everton, but it's no secret that this club is in my heart. I think that together, with Ryan, we can make a real contribution to Manchester United."