Williams, a former all-pro will be reunited with his former offensive coordinator, Mike Martz, who coached him during the 2006 season with Detroit. Williams gained 1,310 yards that year.
He was released by the Dallas Cowboys Thursday and details of the deal with Chicago were not immediately available, theTribune reported.
In the last three seasons in Dallas, Williams had 94 receptions for 1,324 yards and 13 touchdowns.
The Bears' training camp opened Friday at Olivet Nazarene University in Bourbonnais, Ill.