Williamson finished with a two-run total time of one minute 48.61 seconds, more than five seconds behind gold medallist Valerii Redkozubov, of Russia, and 1.79 seconds behind silver medallist Yon Santacana Maiztegui, of Spain.
Conditions on the course were tough, with large ruts; the sound of ski edges on ice could easily be heard.
"This was a choppy rodeo ride," Williamson said of the course. "It's heavy and there are tricky ruts."
Though he came into the second run tied for second place with Slovakia's Jakub Krako, Williamson was not disappointed that he dropped a spot.
"I'm extremely happy," he said. "I just got back from injury; this is my first race of the year. A medal of any colour is exceptional."
Krako missed a gate in the second run and did not finish the race.
The other Canadian in the race, Mac Marcoux, missed a gate on the second gate and also earned a DNF.