Seattle took the lead as early as the 10th minute when Brad Evans shot home a through ball from Fredy Montero.
The visitors doubled their advantage in the 27th minute when Montero found the target with his left foot from the left side of the Chivas penalty box.
Montero added to his tally just seven minutes later, as he turned in Mauro Rosales's pass to make it 3-0.
However, Chivas were given a ray of hope in the 38th minute when the referee awarded them a penalty.
Adam Johansson was adjudged to have fouled Casey Townsend inside the Seattle penalty area, and Juan Agudelo successfully converted the spot kick.
The home side made a strong start to the second half and made it 3-2 on 64 minutes when Miller Bolanos scored from outside the box.
That did not unsettle Seattle, though, as Montero completed his hat-trick just three minutes later to make it 4-2 for the visitors.
Chivas were unlucky not to score their third goal in the 75th minute as Jose Correa's shot hit the right post.
Seattle eventually made it 6-2 through a Samuel Ochoa Oregel header and an Ante Jazic own goal, and bagged maximum points from this Western Conference game.