More than 100 groups, organizations and businesses took part in the parade, which made its way from du Fort Street to Square Phillips.
Montreal police say the parade was calm and peaceful. They had no events to report.
The celebration, often an excuse to indulge in copious amounts of and whiskey and green beer, commemorates Saint Patrick, a Christian missionary who became Ireland's patron saint.
According to Canada's 2006 census, more than 215,000 Montrealers are of Irish descent.