Norway's Finn Haagen Krogh won gold and Italy's Federico Pellegrino captured the silver. It was Valjas' first career World Cup podium appearance in the skate-ski format.
"This is totally unexpected for me with a skate-ski and the race being on this hard of a course, but it turned out to be a great course for me," Valjas said. "I just had a good feeling today and I'm super pumped."
Valjas, a towering six-foot-six Torontonian, led three Canadians into the head-to-head heats with the fastest 30 athletes after qualifying 13th on the 1.4-kilometre track. He later secured one of two lucky loser spots for a shot in the medal round after finishing third in a photo finish at the line.
"I kept telling the wax techs between heats that I was cutting it too close," said Valjas. "I was just tired of making comebacks so I punched it to the front right away in the final."
Darting out of the start gate, Valjas led some of the world's best sprinters around the first of two loops on the highly technical course loaded with twists, turns, a punishing climb and steep downhill to the finish stretch.
The Canadian dropped into the middle of the pack for his final trip around the track to set up another charge to the finish. Racing in fourth spot behind Dario Cologna, Valjas took advantage when the local favourite crashed going up the final climb.
"There is always a bit of luck in sprint racing, but felt like I had third if I kept drafting Cologna," Valjas said. "The downhill finish here was perfect for me. It was a lot of fun racing here beside Cologna. There were so many cowbells, flags and people screaming that it made the atmosphere awesome.
"This is beyond my expectations and I'm just really happy with how things turned out."
Alex Harvey of St-Ferreol-les-Neiges, Que., was 12th and Devon Kershaw, of Sudbury, Ont., was 15th.
Valjas won a bronze and a silver medal in classic-sprint races during his breakout season last year. He also won a bronze medal in a 15-kilometre classic-ski race at the World Cup Finals.
American Kikkan Randall won gold in the women's race, finishing over 50 metres ahead of Ingvild Flugstad Oestberg of Norway. Heidi Weng of Norway won bronze.
There were no Canadian competitors in the women's race.