# By-elections to the 18th Canadian Parliament

By-elections to the 18th Canadian Parliament were held to fill vacancies in the House of Commons of Canada between the 1935 federal election and the 1940 federal election. The Liberal Party of Canada led a majority government for the 18th Canadian Parliament.
31 vacant seats were filled through by-elections.
| By-election | Date | Incumbent | Party | Winner | Party | Cause | Retained |
| Prince | January 2, 1940 | Alfred Edgar MacLean | Liberal | James Layton Ralston | Liberal | Death | Yes |
| Saskatoon City | December 18, 1939 | Alexander MacGillivray Young | Liberal | Walter George Brown | United Reform Movement | Death | No |
| St. James | December 18, 1939 | Fernand Rinfret | Liberal | Eugène Durocher | Liberal | Death | Yes |
| Jacques Cartier | December 18, 1939 | Vital Mallette | Liberal | Elphège Marier | Liberal | Death | Yes |
| Kent | December 11, 1939 | James Rutherford | Liberal | Arthur Lisle Thompson | Liberal | Death | Yes |
| Calgary West | September 18, 1939 | R. B. Bennett | Conservative | Douglas Cunnington | Conservative | Resignation | Yes |
| Brandon | November 14, 1938 | David Wilson Beaubier | Conservative | James Ewen Matthews | Liberal | Death | No |
| London | November 14, 1938 | Frederick Cronyn Betts | Conservative | Robert James Manion | Conservative | Death | Yes |
| Waterloo South | November 14, 1938 | Alexander Edwards | Conservative | Karl Homuth | Conservative | Death | Yes |
| Cartier | November 7, 1938 | Samuel William Jacobs | Liberal | Peter Bercovitch | Liberal | Death | Yes |
| Edmonton East | March 21, 1938 | William Samuel Hall | Social Credit | Orvis A. Kennedy | Social Credit | Death | Yes |
| Argenteuil | February 28, 1938 | George H. Perley | Conservative | Georges Héon | Independent Conservative | Death | No |
| St. John—Albert | February 21, 1938 | William Ryan | Liberal | Allan McAvity | Liberal | Death | Yes |
| St. Henry | January 17, 1938 | Paul Mercier | Liberal | Joseph Arsène Bonnier | Liberal | Appointed a Circuit Court Judge of Montreal | Yes |
| Lotbinière | December 27, 1937 | Joseph-Achille Verville | Liberal | Joseph-Napoléon Francoeur | Liberal | Death | Yes |
| Victoria | November 29, 1937 | Simon Fraser Tolmie | Conservative | Robert Mayhew | Liberal | Death | No |
| Dufferin—Simcoe | November 8, 1937 | William Earl Rowe | Conservative | William Earl Rowe | Conservative | Resignation | Yes |
| Frontenac—Addington | November 1, 1937 | Colin Campbell | Liberal | Angus Neil McCallum | Liberal | Resignation | Yes |
| Cape Breton North and Victoria | October 18, 1937 | Daniel Alexander Cameron | Liberal | Matthew Maclean | Liberal | Death | Yes |
| Renfrew North | April 5, 1937 | Matthew McKay | Liberal | Ralph Warren | Liberal | Death | Yes |
| Hamilton West | March 22, 1937 | Herbert Earl Wilton | Conservative | John Allmond Marsh | Conservative | Death | Yes |
| Bonaventure | March 22, 1937 | Charles Marcil | Liberal | Pierre-Emile Cote | Liberal | Death | Yes |
| Ottawa East | October 26, 1936 | Edgar-Rodolphe-Eugène Chevrier | Liberal | Joseph Albert Pinard | Liberal | Appointed a judge of the High Court of Justice of Ontario | Yes |
| Gloucester | August 17, 1936 | Peter Veniot | Liberal | Clarence Joseph Veniot | Liberal | Death | Yes |
| Wright | August 3, 1936 | Fizalam-William Perras | Liberal | Rodolphe Leduc | Liberal | Death | Yes |
| Victoria | June 8, 1936 | D'Arcy Plunkett | Conservative | Simon Tolmie | Conservative | Death | Yes |
| Antigonish—Guysborough | March 16, 1936 | William Duff | Liberal | J. Ralph Kirk | Liberal | Called to the Senate | Yes |
| Portneuf | January 27, 1936 | Lucien Cannon | Liberal | Pierre Gauthier | Liberal | Appointed a Superior Court Judge of Quebec | Yes |
| Assiniboia | January 6, 1936 | Robert McKenzie | Liberal | James Garfield Gardiner | Liberal | Resignation to provide a seat for Gardiner | Yes |
| Queen's | December 30, 1935 | J. James Larabee | Liberal | Charles Avery Dunning | Liberal | Appointed a Fisheries Protection Officer | Yes |