Placido Maria Schiaffino was born to a family of modest means in Genoa on 5 September 1829.

[1] He studied there and entered the Order of Saint Benedict Olivetana at the monastery of San Girolamo di Quarto a Mare near Genoa in 1846, taking his vows on 17 October 1847.

He studied philosophy at Collegio Romano in 1847, but political turmoil interrupted his education and he became master of novices in the Olivetan monastery of Sicily the next year.

He received his episcopal consecration on 1 September 1878 from Cardinal Raffaele Monaco La Valletta, vicar general of Rome and was named president of the Pontifical Academy of Ecclesiastical Noble on 2 November 1878.

[2] He was named prefect of the Congregation of the Index on 6 April 1888, where he served until he was appointed Vatican Librarian on 20 February 1889.