Dehon acted as stenographer at the First Vatican Council (he was one of four French priests acting as such; his record of the proceedings was published as the "Diario del Concilio Vaticano I" in 1962) and then served as a parish priest at Saint Quentin as a curate from 16 November 1871. He began feeling drawn to communal religious life and on 28 June 1878 - following a pilgrimage to Loreto in 1877 with the Bishop of Soissons Odon Thibaudier - founded the Oblates of the Sacred Heart in which he assumed the religious name "Jean of the Sacred Heart" upon the profession of his vows at the moment of founding; he had begun his novitiate on 31 July 1877 prior to founding.