The Lions signed free-agent linebacker Bobby Carpenter after a workout following practice Wednesday, a league source said.
Carpenter, 28, was a first-round pick (18th overall) by the Cowboys out of Ohio State in 2006. He was most recently with the Dolphins, where he played in five games with 10 tackles. He was released by the Dolphins on Monday.
Carpenter had his most successful season for the Cowboys last year, when he played in all 16 games and recorded 46 tackles and two sacks.