This is a list of by-elections in Canada since Confederation. The list includes Ministerial by-elections which occurred due to the requirement that Members of Parliament recontest their seats upon being appointed to Cabinet. These by-elections were almost always uncontested. This requirement was abolished in 1931.
Notable by-election upsets in Canadian history include the 1949 by-election in Kamouraska where the Liberals, who had won the riding by a 55.8 percentage point margin in the previous general election, were defeated by the Independent Liberal candidate in the by-election; the 1943 Cartier by-election which the Liberals lost to the Labor-Progressive Party's Fred Rose; Deborah Grey's 1989 by-election victory in Beaver River in which she won the Reform Party of Canada's first seat, and Gilles Duceppe's 1990 upset by-election victory in Laurier—Sainte-Marie on behalf of the newly formed Bloc Québécois.
List of federal by-elections in Canada Wikipedia
The Liberal Party of Canada formed a minority government for the 29th Canadian Parliament. No by-elections were held during this Parliament; two seats became vacant during the life of the Parliament, but both remained vacant when the 1974 federal election was called.