He was born at Pointe-Lévy in 1811 and studied at the Petit Séminaire de Québec. He articled in law, was called to the bar in 1839 and set up practice at Quebec City. Lemieux was elected to the Legislative Assembly of the Province of Canada for Dorchester County in an 1847 by-election held because the previously-elected member had been appointed judge. He was reelected in 1848 and 1851. Lemieux played an important role in abolishing seigneurial tenure, serving on the commission formed in 1851 and helping to prepare the legislation that put an end to it. He was elected in the new riding of Lévis in 1854; Lemieux served as Commissioner of Public Works from 1855 to 1856. He was elected again in 1858 and served as Receiver General in that year. Lemieux was defeated by Joseph-Goderic Blanchet in 1861 but was elected to the Legislative Council of the Province of Canada for La Durantaye division in 1862 and served until his death at Lévis in 1864. He had been named bâtonnier for the Quebec bar in 1863.