Tennessee officials announced Sunseri's hiring on Friday.
Sunseri, who's been a part of two national championships in his three seasons with the Crimson Tide, interviewed with Tennessee coach Derek Dooley earlier this week. Sunseri replaces Justin Wilcox, who left to take the defensive coordinator's job at Washington back in December.
"The chance to work with Derek Dooley, who has been around championships and knows what it takes to build an elite program, combined with the rich tradition of the University of Tennessee, makes this opportunity so exciting to me," Sunseri said in a statement. "I am fired up to work with all of the young talent on the defensive side of the ball, and I can't wait to get up to Knoxville and coach them."
Sunseri will receive a three-year deal that will pay him in the range of $800,000 annually, sources told ESPN.com.
Before joining Alabama's staff, Sunseri was the defensive line coach with the NFL's Carolina Panthers for seven seasons. Sunseri has worked under Nick Saban on two occasions. He was on LSU's staff in 2000 as linebackers coach; Dooley also was on that same LSU staff as tight ends coach and recruiting coordinator.
"Sal is an outstanding coach and really did an excellent job with each and every responsibility he had while he was here at the University of Alabama. Although we hate to see Sal go, we understand this is an opportunity for him to grow in this profession and take on the role of defensive coordinator," Alabama coach Nick Saban said in a statement.
The Vols have had five different assistant coaches leave since the end of the season. Sunseri is the third replacement that Dooley has hired, joining offensive line coach Sam Pittman and running backs coach Jay Graham.
"Sal has had unparalleled success over the last decade in not only contributing to team and unit success, but also in his ability to motivate and develop elite individual talent," Dooley said in the same statement. "His combination of defensive knowledge, recruiting success, high-energy personality, ability to connect with players, and personal integrity and character make him an exceptional fit for Tennessee."
Chris Low covers SEC football for ESPN.com.