Andretti Autosport's Hunter-Reay grabbed the lead on lap 57 following a round of pit stops and held on the rest of the way through the 1.75-mile, 11-turn Exhibition Place street course in Toronto.
Hunter-Reay's win also vaulted him into the IndyCar points lead, giving him a 34-point cushion over Will Power, who finished 15th after sustaining a broken wing on his left-front tire.
Charlie Kimball logged a career-best second-place finish at Toronto, while Mike Conway, Tony Kanaan and Oriol Servia completed the Top 5.
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