Anthea Lasis opened the scoring with a power-play goal in the first period for Western. Ally Galloway, Stacey Scott and Kendra Broad added goals in the second. Casey Rosen rounded out the attack with another power-play goal in the third.
Taylor Hough suffered the loss, turning aside 4-of-7 shots in 25:15. Brittany Smrke went the rest of the way and made six saves.
Earlier in the day, Elodie Rousseau-Sirios stopped 27 shots as the sixth-ranked Montreal Carabins edged the No. 4 St. Francis Xavier X-Women 2-1 to claim the bronze medal.
Montreal collected its fourth medal in school history despite the program only being in existence for six seasons— winning the title in 2013 and finishing second in 2012 and 2014.
"The way we build the program right from the start, we aim for excellence and have a very high standard," said Montreal head coach Isabelle Leclaire. "We're trying to build this team like you would build a national team.
"I'm extremely proud that in our six years of existence we've been here five times and have four medals."
Jessica Cormier opened the scoring at 18:22 of the first period for the Carabins and Emmanuelle Passard tacked on the eventual winner 1:22 into the second. Laurence Beaulieu set up both goals for Montreal.
Kara Power ended Rousseau-Sirois' shutout bid when she put the X-Women on the board at 11:21 of the third.
"We were aiming at a gold medal, but on the plus side I'm very proud of the way we played and behaved knowing we could have got to the gold medal," said Leclaire, whose team fell 2-0 to the Western Mustangs in the semifinals.
Sojung Shin turned away 30-of-32 shots for St.FX.
Montreal went 1 for 6 on the power play while the X-Women failed to convert on three chances with the man advantage.
McGill faces Western for gold later today. Earlier, Guelph toppled Moncton 4-1 in the fifth-place match.