Potvin, 27, of Quebec City, fell 6-3 to Mexico's Saul Gutierrez in the final at the Mississauga Sports Centre.
Gutierrez outscored Potvin 3-0 in an extra fourth round for the win.
Povtin won all three of his matches en route to the gold medal, first defeating Brazil's Henrique Precioso 15-5 before earning a 13-11 semifinal win over American Terrence Jennings.
Earlier, Evelyn Gonda of New Westminster, B.C., lost a 10-3 decision to Cuban Yamicel Nunez for bronze in the women's 57-kilogram class.
Gonda, 18, won her first two matches by 12-point margins before dropping a 10-6 semifinal decision to Mexican Paulina Armeria.