Vanderbilt and a rep for Mason are "working on the details" for Mason's contract, and Vanderbilt's John Ingram, a booster and search committee member, told The Tennessean that Mason is indeed James Franklin's replacement.
The school announced the hiring Friday night.
Mason on Friday had a second interview with Vanderbilt and entered the late-week interview process as one of two finalists.
247 Sports reported early Friday that Mason will soon be named the head coach of Vanderbilt. A formal offer had not been made at that point but it turns out Friday's events were a formality.
Stanford loomed large in Vanderbilt's search as the Commodores interviewed Colts offensive coordinator Pep Hamilton, the former Stanford OC, but colleague Bruce Feldman reported that Hamilton has withdrawn from consideration despite being offered the head coaching job. Per sources, Vanderbilt had a private plane set to pick up Hamilton and his family Friday morning, but Hamilton passed to remain with Indianapolis.
The school also has considered Clemson offensive coordinator Chad Morris.
Mason, a Broyles Award finalist, led the nation's third-ranked rushing defense. He was a Minnesota Vikings assistant before joining Stanford in 2010.
Vanderbilt is a much better job than the one Franklin, who's now at Penn State, took over three years ago, but one that comes with expectations after Franklin's staff went 16-4 in the last 20 games. This job is attractive in part because of athletic director David Williams, who is aggressive and willing to spend -- on coaches and facilities.
Vanderbilt has a manageable schedule in 2014 and more than 20 redshirted players from last season that should be ready to contribute.
Herb Hand, a top Franklin assistant, interviewed for the Vandy head job. He could stay with the new coach or follow Franklin to Penn State.
Mason becomes the fifth African-American SEC head coach, and the fourth in the last four offseasons.
This has been a landmark offseason for African-American coaches landing three of the six biggest jobs -- Charlie Strong to Texas, Franklin to Penn State and Mason.