Kenny Miller's fourth-minute goal got the home side off to a great start, and after surviving some long periods of pressure from the Sounders, Darren Mattocks came off the bench to net the insurance tally, which gives Vancouver four wins from its last five matches.
Seattle also entered Saturday's contest on a good run having won three of its previous four games, but the Sounders fell behind inside of four minutes.
Corey Hertzog played a ball over the top from midfield and Miller timed his run perfectly, latching on to the ball inside the penalty area and cutting back past a defender before expertly slotting it inside the right post.
The Whitecaps seemed content to sit back and hit on the counter and it made for a busy evening for goalkeeper Brad Knighton, who came off his line to snuff out Seattle's best chance in the first half, which fell to Eddie Johnson.
Seattle's Lamar Neagle fired over the net from 10 yards just before the break, and he had a cross deflected off the post by Vancouver defender Brad Rusin shortly after halftime.
An acrobatic flick from Obafemi Martins went close as the Sounders continued to pepper the Vancouver net with shots, but Mattocks allowed the home supporters to breathe a bit easier 11 minutes from time.
Gershon Koffie's flicked header from midfield released Mattocks, and he took the ball down off his chest and lofted a clever shot past goalkeeper Michael Gspurning and inside the right post.