The 39-year-old will continue to be available for selection to manager David Moyes during the upcoming Premier League season, but he will also double up as a coach during training sessions at Carrington.
"I got the call [from Moyes] when I was in Turkey [over the summer] doing my coaching badges," he told Inside United.
"My initial thoughts were about how it would affect the playing side of things because I was obviously preparing to play for another year.
"I spoke to a few people and had a think about it and I could only see plus points. I couldn't see any minuses. It's an exciting chance for me and one that I couldn't turn down."
Giggs signed on at Old Trafford as a trainee in 1987.