After ordination Lauzon was sent to Canada, in 1716. From 1716 to 1718 he was Father Pierre-Daniel Richer's assistant at the mission at Lorette. There he studied the Huron and Iroquois languages. He did missionary duty at Sault St. Louis (Caughnawaga) from 1718 to 1731. He made his solemn profession of the four vows at Sault St. Louis on February 2, 1721. He was absent from Sault St. Louis only for the scholastic year 1721-22, when he replaced Father François Le Brun as instructor in the royal school of hydrography in the college at Quebec, as the exhausting labours of the mission had undermined his health.