Marshawn Lynch rushed for 42 yards and two 14.
Lynch carried the ball 20 times and became Seattle's first 1,000-yard rusher since Shaun Alexander in 2005.
Tarvaris Jackson completed 19-of-31 passes for 227 yards and a touchdown for the Seahawks (7-7), who have won three in a row.
Caleb Hanie connected on 10-of-23 passes for 111 yards, a touchdown and three interceptions for the Bears (7-7), who have dropped four straight.
Kahlil Bell carried the ball 15 times for 65 yards. He also caught five passes for 43 yards and a score for Chicago, which was outscored 31-0 in the second half.
Chicago wide receiver Johnny Knox was taken off the field on a stretcher in the first quarter. He suffered a back injury after taking a hard hit.
Down 14-7, the Seahawks started the second half with a five-play, 80-yard scoring drive. Golden Tate and Ben Obomanu caught passes of 33 and 43 yards, respectively, to move the ball to the three. Lynch the rumbled into the end zone from there to make it 14-14.
On the second play of Chicago's ensuing possession, defensive lineman Red Bryant picked off Hanie and went 20 yards the other way for a Seattle touchdown.
Following multiple punts, Seattle took over at its own 46 with 4:37 to go in the third quarter. A defensive pass interference penalty on third down gave the Seahawks a fresh set of downs at the 33. The visitors settled for a 33- yard Steven Hauschka field goal to make it 24-14.
After a Bears three-and-out, Leon Washington had a 36-yard punt return to give Seattle the ball at the Chicago 29. Just six plays later, Michael Robinson caught a two-yard TD pass to make it 31-14 with 12:39 remaining in the fourth.
Brandon Browner's 42-yard interception return for a touchdown made it a 38-14 contest with five minutes left.
After each team went three-and-out to start the game, Chicago took over at its own three-yard line. The Bears lost Knox to injury on the third play. Knox caught a 17-yard pass over the middle of the field before fumbling. Seattle defensive lineman Anthony Hargrove came flying in and hit Knox up high. The wide receiver's head snapped back due to the force of the hit. Knox was taken off the field on a stretcher and the Bears ruled him out with a back injury.
Seattle recovered the ball at Chicago's 22-yard line. Cameron Morrah caught a 21-yard pass on the first play. But the Seahawks lost three yards over the next three plays. Hauschka made a 22-yard field goal, but the Bears were called for a penalty on the play. Lynch capitalized with a two-yard TD run to make it 7-0 with 8:41 left.
Chicago moved the ball to the Seattle 38 before punting on the ensuing possession. On 3rd-and-13 from his own one, Jackson dropped back and was stripped by defensive end Julius Peppers. Israel Idonije recovered the ball in the end zone for the Bears to make it 7-7 with 2:33 to go.
The home team put together a 10-play, 57-yard scoring drive late in the second period. Chicago converted a pair of third downs on the march. On 3rd-and-4 from the Seattle 41, Dane Sanzenbacher caught an eight-yard pass. After three runs by Marion Barber, Hanie hooked up with Bell on a 25-yard score for a 14-7 lead with 1:51 left.
The Seahawks hold a 9-4 advantage in the regular-season series with the Bears...Chicago was without safety Major Wright (shoulder) and defensive tackle Henry Melton (shin)...Barber carried the ball 11 times for 33 yards.