Geno Smith threw a six-yard touchdown pass to DK Metcalf late in the first quarter after a strip-sack by defensive end Mario Edwards Jr.
set up a short drive and Kenneth Walker III scored on a one-yard run just before halftime as the Seahawks (3-1) won their third straight.
A fourth-quarter interception from Quandre Diggs set up a field goal by Jason Myers as Seattle improved to 6-0 at MetLife Stadium, including the franchise’s only Super Bowl win.
Bobby Wagner, Jordyn Brooks, Witherspoon and Uchenna Nwosu each had two sacks. Wagner also had 17 tackles.
Graham Gano kicked a 55-yard field goal for the Giants (1-3), who have played one good half in four games this season and have looked nothing like the team that last year made the playoffs for the first time since 2016.
Seattle were clinging to a 14-3 lead late in third quarter when the Giants moved from their 43 to the Seahawks’ five.
On second and goal, Daniel Jones tried to hit Parris Campbell but the receiver seemed to stumble.
Jones’ pass instead went to Witherspoon, the No. 5 overall pick in the draft, who scored almost untouched crossing from the right side of the field to the left to make it 21-3.
The Giants’ offense has stuttered in the past two games with star running back Saquon Barkley out nursing a high ankle sprain and left tackle Andrew Thomas down with a hamstring injury for three straight weeks.
The Seahawks didn’t do a lot against the Giants’ defense.
The only real drive they had was seven plays, 75 yards just before halftime that was engineered by backup Drew Lock, who replaced Smith after he tweaked a knee and needed an X-ray.
The drive included a 51-yard pass to Noah Fant.
Smith, who returned for the second half, finished 13 of 20 for 110 yards. A bruised Jones was 27 of 34 for 203 yards, while running 10 times for 66 yards.
Seahawks safety Jamal Adams, playing in his first game since tearing his quadriceps in the 2022 season opener, lasted just nine plays before sustaining a concussion when getting kneed in the head while trying to make a tackle on a scrambling Jones. Adams didn’t return.
