The home side started the game strongly and could have take the lead when Sebastian Jaime collected a through ball into the box, but Jon Busch got enough on his chipped effort to divert the ball wide.
Busch kept his side level minutes later when he stretched to punch Sebastian Velasquez's powerful effort from the edge of the box over the bar.
From the resulting corner, San Jose failed to clear their lines as the ball fell to Ned Grabavoy on the edge of the box, and he placed his right-footed shot past Busch into the bottom corner.
Salt Lake doubled their lead in the 30th minute when Luke Mulholland lifted a corner into the six-yard box and Velasquez was unmarked in the area and on hand to poke the ball home from close range.
In the second half, Mulholland advanced forward and reached the edge of the box before firing an effort towards the net, which went inches over the bar.
Adam Jahn tried to drag the visitors back into the match when he received the ball inside the box. The forward beat his man with a neat turn, but he could only send his shot wide of the target.
Yannick Djalo should have got San Jose a goal back minutes later when he latched onto a cross at the back post, but he lost his footing at the vital moment and blasted the ball wide.
The home side had chances to kill the game off, but the two-goal advantage was enough for them to seal the three points and earn their place in the post-season.