# By-elections to the 12th Canadian Parliament

By-elections to the 12th Canadian Parliament were held to elect members of the House of Commons of Canada between the 1911 federal election and the 1917 federal election. The Conservative Party of Canada led a majority government for the 12th Canadian Parliament.
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.
| By-election | Date | Incumbent | Party | Winner | Party | Cause | Retained |
| Dorchester | January 27, 1917 | Albert Sévigny | Conservative | Albert Sévigny | Conservative | Recontested upon appointment as Minister of Inland Revenue | Yes |
| Toronto East | December 14, 1916 | Albert Edward Kemp | Conservative | Albert Edward Kemp | Conservative | Recontested upon appointment as Minister of Militia and Defence | Yes |
| Hochelaga | October 15, 1915 | Louis Coderre | Conservative | Esioff-Léon Patenaude | Conservative | Appointed a judge of the Superior Court of Quebec | Yes |
| Terrebonne | February 8, 1915 | Wilfrid Bruno Nantel | Conservative | Gédéon Rochon | Conservative | Appointed a Railway Commissioner | Yes |
| Westmorland | February 1, 1915 | Henry Emmerson | Liberal | Arthur Bliss Copp | Liberal | Death | Yes |
| Jacques Cartier | February 1, 1915 | Frederick D. Monk | Conservative | Joseph Adélard DesCarries | Conservative | Resignation (ill health) | Yes |
| Prince Albert | February 1, 1915 | James McKay | Conservative | Samuel James Donaldson | Conservative | Appointed a judge of the Supreme Court of Saskatchewan | Yes |
| London | February 1, 1915 | Thomas Beattie | Conservative | William Gray | Conservative | Death | Yes |
| Waterloo South | February 1, 1915 | George Adam Clare | Conservative | Frank Stewart Scott | Conservative | Death | Yes |
| Champlain | November 7, 1914 | Pierre Édouard Blondin | Conservative | Pierre Édouard Blondin | Conservative | Recontested upon appointment as Minister of Inland Revenue | Yes |
| Quebec County | November 7, 1914 | Louis-Philippe Pelletier | Conservative | Thomas Chase-Casgrain | Conservative | Resignation prior to being appointed a judge | Yes |
| York | December 31, 1913 | Oswald Smith Crocket | Conservative | Harry Fulton McLeod | Conservative | Appointed a judge of the Supreme Court of New Brunswick | Yes |
| Lanark South | December 13, 1913 | John Graham Haggart | Conservative | Adelbert Edward Hanna | Conservative | Death | Yes |
| Macdonald | December 13, 1913 | Alexander Morrison | Conservative | Alexander Morrison | Conservative | Election declared void | Yes |
| Bruce South | October 30, 1913 | James J. Donnelly | Conservative | Reuben Eldridge Truax | Liberal | Called to the Senate | No |
| Middlesex East | October 21, 1913 | Peter Elson | Conservative | Samuel Francis Glass | Conservative | Death | Yes |
| Châteauguay | October 11, 1913 | James Pollock Brown | Liberal | James Morris | Conservative | Death | No |
| Portage la Prairie | July 19, 1913 | Arthur Meighen | Conservative | Arthur Meighen | Conservative | Recontested upon appointment as Solicitor General | Yes |
| Hochelaga | November 19, 1912 | Louis Coderre | Conservative | Louis Coderre | Conservative | Recontested upon appointment as Secretary of State for Canada | Yes |
| Carleton | October 30, 1912 | Edward Kidd | Conservative | William Foster Garland | Conservative | Death | Yes |
| Richelieu | October 24, 1912 | Arthur Cardin | Liberal | Arthur Cardin | Liberal | Election declared void | Yes |
| Macdonald | October 12, 1912 | William D. Staples | Conservative | Alexander Morrison | Conservative | Appointed Grain Commissioner for Canada | Yes |
| Simcoe South | June 10, 1912 | Haughton Lennox | Conservative | William Alves Boys | Conservative | Appointed a judge | Yes |
| Kootenay | May 30, 1912 | Arthur Samuel Goodeve | Conservative | Robert Francis Green | Conservative | Appointed a Railway Commissioner | Yes |
| Renfrew South | February 22, 1912 | Thomas Andrew Low | Liberal | George Perry Graham | Liberal | Resignation | Yes |
| Nipissing | November 8, 1911 | George Gordon | Conservative | Francis Cochrane | Conservative | Called to the Senate | Yes |
| Leeds | November 6, 1911 | George Taylor | Conservative | William Thomas White | Conservative | Called to the Senate | Yes |
| Yale—Cariboo | November 4, 1911 | Martin Burrell | Conservative | Martin Burrell | Conservative | Recontested upon appointment as Minister of Agriculture | Yes |
| Halifax | October 27, 1911 | Robert Borden | Conservative | Robert Borden | Conservative | Recontested upon appointment as Prime Minister | Yes |
| Elgin West | October 27, 1911 | Thomas Wilson Crothers | Conservative | Thomas Wilson Crothers | Conservative | Recontested upon appointment as Minister of Labour | Yes |
| St. Anne | October 27, 1911 | Charles Doherty | Conservative | Charles Doherty | Conservative | Recontested upon appointment as Minister of Justice | Yes |
| Toronto North | October 27, 1911 | George Eulas Foster | Conservative | George Eulas Foster | Conservative | Recontested upon appointment as Minister of Trade and Commerce | Yes |
| City and County of St. John | October 27, 1911 | John Waterhouse Daniel | Conservative | John Douglas Hazen | Conservative | Resignation to provide a seat for Hazen | Yes |
| Victoria | October 27, 1911 | Sam Hughes | Liberal-Conservative | Sam Hughes | Liberal-Conservative | Recontested upon appointment as Minister of Militia and Defence | Yes |
| Jacques Cartier | October 27, 1911 | Frederick Debartzch Monk | Conservative | Frederick Debartzch Monk | Conservative | Recontested upon appointment as Minister of Public Works | Yes |
| Terrebonne | October 27, 1911 | Wilfrid Bruno Nantel | Conservative | Wilfrid Bruno Nantel | Conservative | Recontested upon appointment as Minister of Inland Revenue | Yes |
| Quebec County | October 27, 1911 | Louis-Philippe Pelletier | Conservative | Louis-Philippe Pelletier | Conservative | Recontested upon appointment as Postmaster-General | Yes |
| Grenville | October 27, 1911 | John Dowsley Reid | Conservative | John Dowsley Reid | Conservative | Recontested upon appointment as Minister of Customs | Yes |
| Marquette | October 27, 1911 | William James Roche | Conservative | William James Roche | Conservative | Recontested upon appointment as Secretary of State for Canada | Yes |
| Winnipeg | October 27, 1911 | Alexander Haggart | Conservative | Robert Rogers | Conservative | Resignation to provide a seat for Rogers | Yes |