Benoit, who gets $5.5 million a year, reached a preliminary agreement during the general managers' meetings this week in Orlando, Fla.
He had a 1.34 ERA as a setup man for Tampa Bay last season and held opponents to a .147 batting average. Benoit missed 2009 following rotator cuff surgery.
The deal is similar to the one setup man Brandon Lyon signed when he left the Tigers for Houston last offseason.
The Tigers also agreed to terms on a major league contract with right-hander Alberto Alburquerque, who pitched for Double-A Tulsa of the Colorado Rockies' organization last season.
They also purchased the contracts of pitcher Charlie Furbush and shortstop Cale Iorg from Triple-A Toledo, and pitchers Lester Oliveros, Jose Ortega, Brayan Villarreal and Duane Below from Double-A Erie.