 In 1863, Gérin-Lajoie was elected to the Legislative Assembly of the Province of Canada for Saint-Maurice as a member of the Parti rouge.He opposed Confederation, but was elected to the federal parliament in 1874 running as a Liberal.In 1878, he was named superintendent of Public Works for Saint-Maurice and he served in that function until his death at Trois-Rivières on November 6, 1895.