 Serafini was ordained to the priesthood on 21 October 1877.From 1877 to 1892, he was a member of the Benedictine community at the abbey of Subiaco, later serving as its master of novices (1889–1891) and lector of theology.After being named prior of the St Scholastica monastery, Serafini became the general procurator of his religious order in Rome in 1892.