The Packers looked to be heading to a crucial victory over their NFC North divisional rivals after opening up a 16-6 lead with just over five minutes remaining in the fourth quarter.
Green Bay backup quarterback Malik Willis had played half the game after starter Jordan Love was out with a concussion. He put the Packers up 13-6 after throwing a dime to receiver Romeo Doubs down the sideline for a touchdown.
But after a Cairo Santos field goal reduced the deficit to 16-9, the Bears regained possession with a successful onside kick.
Quarterback Caleb Williams tossed a touchdown pass to Jahdae Walker with just over 20 seconds remaining to tie the game 16-16, sending it to OT.
After stopping Green Bay's first drive in overtime, the Bears then walked it off with Williams' 46-yard touchdown pass to DJ Moore.
The Bears will clinch their playoff berth if the Detroit Lions lose to the Pittsburgh Steelers on Sunday. They currently sit at 11-4 on the season as they expand their lead in the NFC North.