An eight-year veteran, Acho made 25 starts in four seasons with the Bears and had four sacks, three pass breakups and three forced fumbles. He missed the final 12 games last year because of a torn pectoral muscle.
Acho helped coordinate the Bears' social justice initiatives and has worked with several charities, most notably Living Hope Christian Ministries. That organization founded by his parents in 1989 provides medical services in Nigeria.
The Bears announced the move on Tuesday.