The Indianapolis Colts and former Tennessee quarterback announced the gift Saturday during a dedication of the Volunteers' locker room that bears his name. The Mannings also gave $1 million for that facility, which was completed last year.
"Tennessee has been such an important part of my life," he said. "I want the future student-athletes that are coming here to have the best support around them. I still want us to be able to attract the best student-athletes."
Tennessee is scheduled to break ground on the $39 million, 132,000-square-foot training facility in November.
The training facilities were top-notch when Manning arrived on the Knoxville campus in 1994. Since then other schools have improved their facilities, and Manning said he thought the renovations would be key to staying competitive in recruiting.
"Peyton Manning represents everything that's right about the student-athlete process," Tennessee athletic director Mike Hamilton said.
After leading Tennessee to two Southeastern Conference championships, Manning was a No. 1 pick in the NFL draft. He has twice been named the NFL's MVP.
Manning was on campus Saturday for the Vols' opener against Western Kentucky, a 63-7 rout for new coach Lane Kiffin.
Manning said game day had a different feel to it without his Tennessee coach, Phillip Fulmer, on the sidelines. Fulmer was fired in the middle of the Vols' 2008 season, which they finished 5-7.
"Change is something you have to adjust to," he said. "I think it will be an adjustment for a lot of people -- certainly it will for me. It's important to the players that they get off to the season on the right note and put this offseason of change behind them and get to playing some football."