Cain will join the Bears for a third time. He first played for the club from 2004-05, mostly on special teams and as a backup linebacker, then again last year for two games as a long snapper.
Overall, Cain has appeared in 83 NFL games with Chicago, Tennessee (2006) and Jacksonville (2009-12). All but eight of those games came as a long snapper.
The Bears cut long snapper Brandon Hartson on Sunday.
Chicago also named its 10-man practice squad, inking wide receivers Josh Bellamy and Rashad Ross, offensive linemen Taylor Boggs and Ryan Groy, defensive linemen Brandon Dunn and Roy Philon, cornerbacks Isaiah Frey, Al Louis-Jean and Terrance Mitchell and linebacker DeDe Lattimore to the unit.