Bell played 20 games for the Bears the last three seasons and made three starts, including the final two last season after Matt Forte sprained his knee. Bell would have been Chicago's third-string back behind Forte and Michael Bush.
Bell ran for 557 yards on 119 attempts and also caught 20 passes for 137 yards and a TD with the Bears.
Lorenzo Booker and Armando Allen are expected to compete for the third-string running back job now that Bell is gone.
A dispute over a pay cut is what's believed to have led to the parting of the ways.