The native of Sault Ste. Marie, Ont., guided by his brother BJ, captured silver in the men's super-G on Thursday, a day after winning gold in the downhill.
Marcoux finished in one minute 24.04 seconds, .41 seconds behind winner Ivan Fransev of Russia. Slovakia's Miroslav Haraus was third in 1:24.81.
"We got off to a little bit of a slow start, then coming down into the speed sections we started to pick it up from there," said BJ Marcoux. "We raced pretty solid and we ended up in second place."
It's been a stellar season for the 17-year-old Mac Marcoux, who has won eight World Cup medals, including five gold, to collect Crystal Globe as the overall champion.
Six other Canadian skiers were in action Thursday.
In the men's standing downhill, Matt Hallat of Coquitlam, B.C., was 13th while Kirk Schornstein of Spruce Grove, Alta., finished 15th. Braydon Luscombe of Duncan, B.C., did not finish.
In the men's sitting super-G, Kurt Oatway of Calgary was 17th.
On the women's side, Toronto's Erin Latimer was seventh in the women's standing super-G while Calgary's Alana Ramsay was seventh.