Taoiseach Leo Varadkar, Ireland's first gay PM, attended Sunday's event with his Canadian counterpart Justin Trudeau.
The leaders also held talks, where they discussed a range of issues, including Brexit and abortion.
Mr Varadkar and Mr Trudeau met for the first time when the Canadian prime minister visited Ireland in July.
Mr Trudeau said the taoiseach was the first foreign leader to take part in a pride event in Canada.
Speaking at a joint news conference after the bilateral talks, Mr Varadkar said he discussed the issue of abortion with Mr Trudeau. He stated that he wanted to hold a referendum on the Eighth Amendment in the first half of next year.
The Eighth Amendment to the Irish constitution was passed in 1983 and granted a foetus equal right to life as its mother, effectively outlawing abortion.
Irish Prime Minister Leo Varadkar began his three-day visit to Canada by taking part in the Montreal Pride Parade.