After a year away at Mont-Tremblant, the Canadian GP returned to Mosport Park a fortnight after the Italian GP. The usual field was bolstered by third cars being run by Lotus (a four-wheel-drive 63 for John Miles), Matra (a four-wheel-drive car for Johnny Servoz-Gavin) and BRM (for local driver Bill Brack). US driver Peter Lovely had bought a Lotus 49 while Al Pease and John Cordts turned up with an old Brabham and an old Eagle. Ferrari had only one car, which was entered for Pedro Rodríguez by Luigi Chinetti's North American Racing Team.

Jacky Ickx was in fine form and qualified his Brabham on pole position with Jean-Pierre Beltoise's Matra alongside and Jochen Rindt's Lotus completed the front row. The new World Champion Jackie Stewart was on the second row with Denny Hulme (McLaren) wile the third row boasted Jack Brabham (Brabham), Graham Hill (Lotus) and Jo Siffert (Walker-Durlacher Lotus).

Rindt took the lead at the start ahead of Ickx, Beltoise and Stewart but the Scot moved quickly up to pass Beltoise on the second lap, Ickx on the fifth lap and he took the lead from Rindt on lap six. Ickx passed Rindt two laps later and closed on Stewart and the two began a dice for the lead. Rindt ran third while Beltoise led a pack battling for fourth until he collided with Pease as he lapped the Canadian for the second time.

On lap 33 as the leaders lapped Pease for the fourth time, Ickx challenged Stewart for the lead. The two cars collided and spun. Stewart was unable to restart his car and so Ickx was able to take the lead and won the race, while Brabham came through to second, passing Rindt on lap 60 to make it a Brabham 1-2. Pease was eventually black-flagged for being uncompetitive.