He was received into the diaconate in Bagnoregio on 14 March 1767. Strambi was ordained to the priesthood on 19 December 1767 and then returned to Rome to further his theological studies. Here he was noted for his studies of the life and works of Saint Thomas Aquinas. He still felt called to the Passionists and made several trips to see Paul of the Cross to beg to be admitted into the order. In September 1768 the founder relented and Strambi commenced his novitiate assuming the name in secolo Vincenzo Maria di San Paolo. His parents were not too pleased with this and his father objected to the decision citing his son's frail health as a sign that Strambi would die due to the rigid penances. He made his profession on 24 September 1769 and continued his studies with a particular emphasis on the Church Fathers and on Sacred Scripture.