The Milwaukee Journal Sentinel reported that Lenon will receive a signing bonus of about $1 million as part of the deal. No specific terms were available.
The versatile Lenon started a career-high 12 games last season, seven at strong-side linebacker and five at weak-side. He began the season as a reserve but his playing time increased due to injuries to Na'il Diggs and Robert Thomas.
Lenon met with the Buffalo Bills late last week before traveling to Detroit on Tuesday.
Lenon began his tenure in Green Bay late in 2001 when he was signed to the practice squad. The University of Richmond product had played with the XFL's Memphis Maniacs earlier in 2001. Lenon also played in NFL Europe in the spring of 2002.
In 2004, Lenon started his first career game as the fourth linebacker when the Packers defense opened in a 3-4 alignment in the opener at Carolina (9/13), but broke his thumb. He played the next five games with a cast but still contributed on defense and special teams.
Without Lenon and Diggs, who was released on March 1, the Packers have only Nick Barnett as their starter. It appears that the Packers will not re-sign unrestricted free agent Robert Thomas, who finished the season on injured reserve.
Roy Manning, who improved as the season progressed and started two games, is one of two reserves currently on the roster. The other is Brady Poppinga, but he is coming off an ACL injury and may not be ready to play early in the season.
Green Bay has met with Cleveland Browns free agent Ben Taylor, but he has not signed a contract.