Seniors Alex Roelse and Matt Farmer led the top-seeded Bruins (21-4) with two goals each. Redshirt sophomore goalkeeper Alex Wolf made 10 saves.
The title is UCLA's 11th in program history and the 114th NCAA championship for the university.
The third-seeded Trojans (27-4) got goals from five players. USC led 2-1 after the first period and 3-2 at halftime. UCLA took a 5-4 lead into the final period.
USC played in its 13th consecutive NCAA championship match, but lost for the fourth year in a row.