Acho, 27, worked his way into the Bears' starting lineup last year after battling an illness for much of the preseason. He played in 15 games (seven starts), recording 60 tackles (based on coaches' review), three tackles for loss, one forced fumble and one fumble recovery.
A former starter with the Arizona Cardinals, he is an experienced 3-4 outside linebacker and a valuable contributor on special teams, recording eight tackles for the Bears unit in 2015 -- the fourth most on the team. Acho has 22 career stops on special teams.
He has played in 66 career games between Chicago and Arizona.
Acho is the ninth Bears unrestricted free agent to re-sign with the club in March.