Leman, from Calgary, was in the four-man big final with Toronto's Kevin Drury.
Humphries, the two-time defending Olympic gold medallist from 2010 and 2014, and George moved from fifth to third following the third run.
Brady Leman earned Olympic gold for Canada, beating Marc Bischofberger of Switzerland and Russian athlete Sergey Ridzik.
Leman meanwhile had the eighth fastest time in seeding, placed second in heat two of the elimination round behind Bischofberger, ahead of Bischofberger to win the first heat of the quarterfinals and then beat Bischofberger again in the semi-finals.
"I broke my leg the day before competition in Vancouver and then just missing the podium in Sochi was kind of bittersweet. Right now we are the best nation in the world in ski cross and have been for a couple of years", Leman said after claiming Canada's third gold medal from a possible five in ski cross events at the Olympics. Because Drury lost a ski he wasn't allowed to try and get down the hill for a potential bronze.
Four years ago in Sochi, Canada's Brady Leman crashed out in the men's Olympic ski cross final, leaving the three French skiers alongside him to cruise to a podium clean-sweep.
Ridzik managed to finish the race for the bronze.