It was the first medal of the season for Serwa, who is the reigning world champion. The Kelowna, B.C., native dominated her quarter-final and semifinal before moving from last to first in a final which saw Switzerland's Katrin Mueller spin out and French veteran Ophelie David disqualified.
Simmerling, of West Vancouver, B.C., stayed out of trouble to claim her first career World Cup podium.
Serwa is third in the ski cross standings with 195 points behind Fanny Smith of Switzerland (336) and Norway's Marte Hoeie Gjefsen (207).
On the men's side, Calgary's Brady Leman failed to reach the podium for a third straight time and finished fifth. He has two silvers so far this season.
Louis-Pierre Helie of Berthierville, Que., finished eighth.
In ski cross, four skiers race each other down a course of jumps and bumps.