In 1847 the Holy See created the Diocese of Saint Boniface, and named Provencher its first bishop. In June 1850, Taché was named titular bishop of Arathia and Provencher's coadjutor bishop, when he was still only 27 years old. He did not receive the news of his appointment, however, until January 1851. He was consecrated a bishop on 23 November 1851 in Marseille, France, by St. Eugene de Mazenod, founder of the Missionary Oblates. Provencher died on 7 June 1853, and Taché automatically succeeded him as the Bishop of St. Boniface.