"Thirty seven-six just shows what we're capable of, but we're a lot better than that," Grossman said. "They're a lot better than they played tonight and we realize that. ... We realize we may face them down the road at some point, and we're glad we got the win."
Grossman had another solid performance, completing 17 of 31 passes with two touchdowns and no interceptions, and the Bears improved to 4-0 for the first time since 1991.
Bernard Berrian had three receptions for a career-high 108 yards and a touchdown.
The Bears also got their running game going after three sluggish performances, with Thomas Jones rushing for 98 yards and two touchdowns.
And the league's fourth-ranked defense shut down a Seahawks team that was missing injured running back Shaun Alexander.
"We definitely sent a message," Briggs said. "We're out to send a message every week. Every week, we gain another believer."
With the Bears leading 10-3, Manning intercepted Hasselbeck twice in the second quarter to set up a field goal and touchdown.
"There is really no need for that," Hasselbeck said. "I've got to be smarter. We have to stick to our gameplan and handle that stuff better. We didn't communicate well and didn't execute well."
Maurice Morris started for Alexander and carried 11 times for 35 yards.
The league MVP, Alexander had been bothered by a bruised bone in his left foot before it cracked during last week's win over the Giants. Still, he hoped to play, saying the power of prayer had healed him and even jumping around for coach Mike Holmgren. A second round of tests on Wednesday showed the bone was still broken, so he sat for the first time since being drafted in 2000, and Morris made the fifth start of his career.
The Seattle defense took a hit in the second quarter, when safety Michael Boulware suffered a concussion while breaking up a pass intended for Chicago's John Gilmore at the Seattle 1.
"I always think Shaun Alexander would have made a difference," Seattle coach Mike Holmgren said. "He's the MVP of the league. This is the most pressure I think Matt has felt in awhile."
Sunday's game was the ninth between the two teams and their first in three years.
Seattle opened the scoring with a 23-yard field goal by Josh Brown on its second possession, and the Bears wasted no time responding. They drove 69 yards, with Grossman completing six of seven passes for 57 yards. He hit Muhsin Muhammad for 14 yards on the first play and found Muhammad cutting toward the middle of the end zone for a 9-yard touchdown that made it 7-3 with 2:27 left in the quarter.
"If you need time, it's going to be hard to find with our defensive line," Briggs said. "You like that rhyme?"
The pressure created opportunities for the defensive backs -- most notably, Manning.
On Tuesday, he pleaded no contest to a felony assault charge stemming from an incident at a restaurant in Los Angeles. But he put aside his legal issues on Sunday.
Manning picked off a short pass intended for Deion Branch at the Chicago 25 and returned it 39 yards before Hasselbeck knocked him out of bounds at the Seahawks 36 about 5 minutes into the second quarter. That led to a 20-yard field goal by Gould that made it 13-3.
"This game is big," Briggs said. "Big. Big. This is the way we've got to play at home."
Holmgren said Boulware should be ready to play next week. ... Berrian has caught three passes of 40 or more yards this season.