Teams should probably stop surrendering set pieces to Toronto FC.
The 41st-minute tally gave Toronto the lead at Stade Saputo before Jozy Altidore made it 2-0 in the 52nd minute.
While Ignacio Piatti pulled one back in stoppage time, Giovinco converted a skilled volley to clinch the result for TFC.
Toronto improved to 16-3-8 with the win, extending its lead atop the Supporters' Shield standings to nine points. Montreal dropped to 10-9-6, leaving the Impact in seventh — behind Atlanta United on goal differential for the final Eastern Conference playoff slot.