The sin-binning of captain Jamie Cudmore ultimately proved costly for Canada as Ireland scored three tries during his absence, and another four afterwards, in a Pool D 50-7 victory at the Millennium Stadium in Cardiff on Saturday.
Yellow-carded for an offence at a maul close to their own try-line, Canada were immediately on the back foot as Sean O'Brien, Iain Henderson and Jonathan Sexton dotted down.
Another try followed for Dave Kearney, while man-of-the-match Sexton also contributed nine points via a penalty and three conversions, to give the Irish a 29-0 lead at half-time.
Shortly after the break, Ireland captain Paul O'Connell was sent to the sin bin, but in stark contrast to Cudmore's card, the Irish defence held firm and no points were conceded.
Ireland, looking sharp and clinical, then ran in second-half tries through Sean Cronin, Rob Kearney and Jared Payne, all converted by Ian Madigan.
DTH van der Merwe scored Canada's consolation try, with Nathan Hirayama converting.