Hamelin, from Sainte-Julie, Que., finished second in the men's 1,500 metres while St-Gelais, from Saint-Felicien, Que., was second in the women's 500 metres.
Hamelin was just behind South Korea's Sin Da Woon, who won in two minutes 16.943 seconds. Hamelin was next in 2:17.041 and John-Henry Krueger of the United States was third in 2:17.169.
"I skated well in the final, I was able to manage my energy level well," said Hamelin. "The Korean skater was in front with four laps to go and he was able to finish it off with strong skating, while I had just enough legs to be able to stay with him. So I mainly worked on protecting my position."
It was Hamelin's second medal of the World Cup season. He won a silver in the 1,500 at the season-opening event in Salt Lake City.
St-Gelais finished second behind China's Fan Kexin, who won in 43.272 seconds. The Canadian was next in 43.361 and South Korea's Kim Alang was third in 43.458.
"I wanted to try to do something to overtake the Chinese skater, but I still can't find that switch, it seems, that would allow me to react at the right time," said St-Gelais. "I thought about it, I saw the openings and I adapted my line to be able to do it. But I wasn't able to take advantage of it.
"But I was right there, I was able to stay with her. I just need to find a way to push it a little more."
It was her fourth individual medal of the season. Also Saturday, both Canadian relay teams qualified for Sunday's finals.