Cutler, who overcame an interception return for a touchdown and a fumble to throw for 345 yards, calmly led the Bears on the winning 10-play, 80-yard drive after the Chargers opened a 19-14 lead on rookie Josh Lambo's 22-yard field goal.
It was the first lead for Chicago, which scored 15 points in the fourth quarter.
Cutler's two TD passes broke the franchise record, giving him 139 with the Bears. He had been tied with Hall of Famer Sid Luckman.
The Bears (3-5) snapped a two-game losing streak. San Diego (2-7) lost its fifth straight.
Cutler never wavered in another tight game for Chicago. He continually attacked San Diego's depleted secondary, completing 27 of 40 passes.
Two plays before the TD throw to Miller, Cutler was hit and still completed a 12-yard pass to Alshon Jeffery on third-and-6.
San Diego's Philip Rivers was 26 of 42 for 280 yards. It was the first time in six games that he didn't throw for more than 300.
The Bears had a rough first half, but the Chargers couldn't put them away.
Cutler lost a fumble on a sack and then made an off-the-mark throw to Jeffery, which second-year cornerback Jason Verrett intercepted and returned 68 yards for a 13-0 lead.
The Chargers suffered even more injuries.
Verrett hurt his groin one play after his pick-six and came out, but remained on the sideline. Cornerback Patrick Robinson left with a neck injury.
Wide receiver Malcom Floyd, who is playing his last season, injured his left shoulder while diving trying to make a catch. Eight days earlier, San Diego's Keenan Allen, one of the NFL's leading receivers, suffered a season-ending lacerated kidney when he landed hard at the end of a spectacular touchdown catch in a loss at Baltimore.
Cutler broke the franchise record for touchdown passes when he found Martellus Bennett for a 1-yard score midway through the second quarter.
Cutler had been tied with Hall of Famer Sid Luckman with 137 with the Bears. Cutler began his career with the Broncos. Luckman threw his final touchdown pass as a member of the Bears on Sept. 17, 1950.
Langford scored on a 1-yard run early in the fourth quarter to start Chicago's comeback.