Vancouver (6-5-4) jumped into the top half of the Western Conference and, with 22 points, moved within six of first-place Dallas. The Whitecaps have earned 13 points in their last six games and have won back-to-back contests for the first time this season.
Chivas USA (3-9-2) has lost six straight and is winless in nine games.
Sanvezzo assisted on a goal by Jordan Harvey that tied the game in first-half stoppage time, then put Vancouver in front moments before intermission.
He delivered an insurance goal in the 81st minute by jumping on a loose ball in the penalty area and beating Dan Kennedy with a shot through traffic.