Rivers, the younger brother of San Diego Chargers quarterback Philip Rivers, has used only two seasons of eligibility after taking a redshirt year at LSU in 2011.
Vanderbilt announced that the 6-foot-6, 230-pound Rivers is enrolling in a post-graduate program at the university's Divinity School this summer.
''I'm happy for Stephen and looking forward to having him join our program,'' Commodores head coach Derek Mason said. ''Stephen brings both ability and experience to our team, and he fits the offensive system we will run under [offensive coordinator] Karl Dorrell. I'm looking forward to seeing great competition at the quarterback position this August.''
Rivers will compete with sophomore Patton Robinette and redshirt freshman Johnny McCrary. Robinnette is the only quarterback on the roster who has taken meaningful snaps for the Commodores. He started three games late last season, including a victory at Florida and a victory against Houston in the BBVA Compass Bowl.
Rivers spent 2012 as Zach Mettenberger's backup, seeing limited action in four games. He entered 2013 expecting to be Mettenberger's backup again, but fell behind Anthony Jennings in the depth chart.
Rivers graduated from LSU this spring and was granted a release to play immediately at another school.
Rivers says he hopes to eventually play in the NFL and has been looking to join a program where he'd be a candidate to start.