The Sounders came close to taking the lead in the 21st minute when Obafemi Martins weaved his way through two defenders and drilled an effort at goal, but Jaime Penedo made a brilliant one-handed save.
Martins threatened again minutes later when he managed to control the ball from an awkward height and knocked it into stride. However, two defenders closed in on him and did just enough to force him to skew his shot wide.
Los Angeles took the lead on the stroke of half time when Dan Gargan's cross was poorly cleared by the Sounders defence, and Baggio Husidic's effort on the half volley from the edge of the area found the bottom corner.
In the second half, Penedo denied Martins again as he raided through on goal after a neat one-two with Clint Dempsey, but the keeper did well to come out and narrow the angle to make the block.
However, Dempsey brought his side back into the game when DeAndre Yedlin's cross was deflected into the path of the forward at the back post, and he made no mistake firing a left-footed volley past Penedo.
Seattle found their equaliser in the 73rd minute when Martins released the run of the unmarked Lamar Neagle, who sprinted into the box and blasted an effort through the legs of Penedo.
Late in the game Omar Gonzalez was given a red card for a second bookable offence following a poor challenge on Gonzalo Pineda, but the Sounders didn't have enough time to take advantage as the match ended in a stalemate.