Marshawn Lynch ran for 131 yards, and Russell Wilson completed 15 of 26 passes for 187 yards and ran eight times for 67 yards for the Seahawks, who broke an eight-game postseason losing streak away from home.
Seattle will visit the top-seeded Atlanta Falcons next Sunday.
Lynch’s 27-yard run with 7:08 remaining gave the Seahawks (12-5) the lead. On Washington’s next series, Griffin reinjured the right knee he sprained about a month ago while trying to field a bad shotgun snap.
The knee buckled badly, and the Seahawks recovered the fumble and kicked an insurance field goal.
Kirk Cousins replaced Griffin, but Washington (10-7) was unable to come back.
RG3 three two 4-yard touchdown passes in his first career playoff game to give the Redskins a 14-0 lead before the Seahawks closed to 14-13 through three quarters.
Griffin capped the Redskins’ only two drives of the first quarter against the NFL’s top-rated scoring defense with short tosses to running back Evan Royster and tight end Logan Paulsen.
The Seahawks allowed 15.3 points per game this season and the 14-point deficit was their largest of the season.
The second quarter belonged to Seattle, with Wilson throwing a 4-yard TD pass to running back Michael Robinson and Steve Hauschka kicking a pair of field goals.
Hauschka’s 32-yard field goal 2:55 into the second quarter made in 14-3 and his second kick, a 29-yarder as the half expired, pulled the Seahawks with a point.
The right-footed Hauschska was playing with a left ankle injury and limped off the field to the locker room.
Seattle maintained its offensive efficiency starting the third quarter, driving 69 yards to the Redskins 1, but Lynch fumbled and Washington’s Jarvis Jenkins recovered.
After forcing a Redskins punt, Wilson moved the Seahawks to the Washington 28, but overthrew Doug Baldwin in the end zone. Wilson was sacked on the next play, moving the ball back to the 37. With Hauschka limited, Seattle punted.
Griffin was 10 of 17 for 84 yards, but after the first quarter he threw for only 16 yards plus an interception. The Redskins quarterback also ran three times for 12 yards.
On the Redskins’ second drive of the game, the Redskins’ sensational rookie quarterback fell awkwardly while backpedaling on a pass and came up limping. But he stayed in the game. He sprained his right knee in Week 14 and sported a brace for the third straight game.
Lynch rushed 14 times for 79 yards in the first half, including 41 on the drive which ended with his fumble. In the second quarter, he scooped up a Wilson fumble and raced for 19 yards, leading to the Seahawks touchdown.
Rookie Alfred Morris, the league’s second-leading rusher, had 72 yards — 34 of them on four carries during Washington’s opening drive that resulted in the TD pass to Royster.
Paulsen’s touchdown catch finished off an 11-play, 54-yard drive in 5:58.
Washington’s offense slowed in the second quarter with two drives resulting in a punt and an interception by Seattle Pro Bowl safety Earl Thomas.
Seattle was moving the ball in the first quarter, but a promising drive ended when the Redskins’ Stephen Bowen and London Fletcher combined to sack Wilson on third-and-2. It was one of two sacks for the Redskins in the quarter.
The playoff meeting between the two teams was the third, but first outside Seattle. The Seahawks won 20-10 in January 2006, and 35-14 in January 2008. Those were the last two postseason games played by the Redskins, who entered the playoffs on an NFC-best seven-game winning streak.
Seattle came into the playoffs with a five-game winning streak, outscoring opponents 193-60. But they were 3-5 on the road and had lost eight straight road playoff games. Their only road playoff win came in their first postseason road game, Dec. 31, 1983, at Miami.
And now they have another.