Rafael Nadal is a four-time champion at the Rogers Cup.
The top-seeded Spaniard defeated Stefanos Tsitsipas 6-2, 7-6 (4) to win the men's singles title at Aviva Centre.
Nadal converted on his first match point of the tiebreaker to win his 33rd career A-T-P World Tour Masters 1000 crown.
Tsitsipas, who beat four top-10 players to reach his first career Masters 1000 final, had no real answer for the world No. 1.
Simona Halep is now a two-time winner at the Rogers Cup.
The world's top-ranked player defeated third-seeded Sloane Stephens 7-6 (6), 3-6, 6-4 in a see-saw battle that featured 15 service breaks eight for Stephens, seven for Halep at a steaming hot I-G-A Stadium.
The 26-year-old also won when the event was last held in Montreal in 2016.