 He taught at the Catholic University of Angers from 1879 to 1882 and made his final vows as a Jesuit on 2 February 1883, while teaching at the Jesuit Scholasticate on Jersey.In 1885, Billot became a professor of dogmatic theology at the Pontifical Gregorian University in Rome.In addition his academic post, he was named a consultor to the Holy Office on 19 June 1909.