# By-elections to the 21st Canadian Parliament

By-elections to the 21st Canadian Parliament were held to fill vacancies in the House of Commons of Canada between the 1949 federal election and the 1953 federal election. The Liberal Party of Canada led a majority government for the 21st Canadian Parliament.
30 vacant seats were filled through by-elections.
| By-election | Date | Incumbent | Party | Winner | Party | Cause | Retained |
| Outremont—St-Jean | October 6, 1952 | Édouard-G. Rinfret | Liberal | Romuald Bourque | Liberal | Appointed a Judge of the Court of Queen's Bench of Quebec | Yes |
| Richelieu—Verchères | October 6, 1952 | Gérard Cournoyer | Liberal | Lucien Cardin | Liberal | Resignation | Yes |
| Ontario | May 26, 1952 | Walter Cunningham Thomson | Liberal | Michael Starr | Progressive Conservative | Resignation | No |
| Gloucester | May 26, 1952 | Clovis-Thomas Richard | Liberal | Albany M. Robichaud | Progressive Conservative | Resignation | No |
| Victoria—Carleton | May 26, 1952 | Heber Harold Hatfield | Progressive Conservative | Gage W. Montgomery | Progressive Conservative | Death | Yes |
| Brome—Missisquoi | May 26, 1952 | Henri A. Gosselin | Liberal | Joseph-Léon Deslières | Liberal | Death | Yes |
| Roberval | May 26, 1952 | Joseph-Alfred Dion | Liberal | Paul-Henri Spence | Progressive Conservative | Appointed a Superior Court Judge of Quebec | No |
| Waterloo North | May 26, 1952 | Louis Orville Breithaupt | Liberal | Norman C. Schneider | Liberal | Appointed Lieutenant Governor of Ontario | Yes |
| Calgary West | December 10, 1951 | Arthur LeRoy Smith | Progressive Conservative | Carl Olof Nickle | Progressive Conservative | Resignation | Yes |
| Brandon | June 25, 1951 | James Ewen Matthews | Liberal | Walter Dinsdale | Progressive Conservative | Death | No |
| Queen's | June 25, 1951 | J. Lester Douglas | Liberal | J. Angus MacLean | Progressive Conservative | Death | No |
| Waterloo South | June 25, 1951 | Karl Homuth | Progressive Conservative | Howie Meeker | Progressive Conservative | Death | Yes |
| Winnipeg South Centre | June 25, 1951 | Ralph Maybank | Liberal | Gordon Churchill | Progressive Conservative | Resignation | No |
| Rimouski | October 16, 1950 | Gleason Belzile | Liberal | Joseph-Hervé Rousseau | Independent Liberal | Death | No |
| St. Mary | October 16, 1950 | Gaspard Fauteux | Liberal | Hector Dupuis | Liberal | Resignation | Yes |
| Welland | October 16, 1950 | Humphrey Mitchell | Liberal | William H. McMillan | Liberal | Death | Yes |
| Joliette—L'Assomption—Montcalm | October 3, 1950 | Georges-Émile Lapalme | Liberal | Maurice Breton | Liberal | Resignation | Yes |
| Annapolis—Kings | June 19, 1950 | Angus Alexander Elderkin | Liberal | George Clyde Nowlan | Progressive Conservative | Election declared void | No |
| Cartier | June 19, 1950 | Maurice Hartt | Liberal | Leon Crestohl | Liberal | Death | Yes |
| Halifax | June 19, 1950 | Gordon B. Isnor | Liberal | Sam Balcom | Liberal | Called to the Senate | Yes |
| Broadview | May 15, 1950 | Thomas Langton Church | Progressive Conservative | George Hees | Progressive Conservative | Death | Yes |
| Hamilton West | May 15, 1950 | Colin W. G. Gibson | Liberal | Ellen Fairclough | Progressive Conservative | Appointed a Judge of the Supreme Court of Ontario | No |
| Gatineau | October 24, 1949 | Léon-Joseph Raymond | Liberal | Joseph-Célestin Nadon | Liberal | Appointed Clerk of the House of Commons | Yes |
| Kamouraska | October 24, 1949 | Eugène Marquis | Liberal | Arthur Massé | Independent Liberal | Appointed a Superior Court Judge of Quebec | No |
| Laurier | October 24, 1949 | Ernest Bertrand | Liberal | J.-Eugène Lefrancois | Liberal | Appointed a Judge of the Court of King's Bench of Quebec | Yes |
| Mercier | October 24, 1949 | Joseph Jean | Liberal | Marcel Monette | Liberal | Appointed a Judge of the Supreme Court of the District of Montreal | Yes |
| Greenwood | October 24, 1949 | J. Ernest McMillin | Progressive Conservative | James Macdonnell | Progressive Conservative | Death | Yes |
| New Westminster | October 24, 1949 | Tom Reid | Liberal | William Malcolm Mott | Liberal | Called to the Senate | Yes |
| Restigouche—Madawaska | October 24, 1949 | Benoît Michaud | Liberal | Paul-Léon Dubé | Independent Liberal | Death | No |
| Jacques Cartier | October 4, 1949 | Elphège Marier | Liberal | Edgar Leduc | Independent | Appointed a Superior Court Judge of Quebec | No |