Born in Pontremoli, Chiarlo studied at the seminary in Lucca and the Pontifical University of St. Thomas Aquinas (Angelicum) in Rome before being ordained to the priesthood on 28 May 1904.
Chiarlo's early life was marked by his birth in Pontremoli, followed by his studies at a seminary in Lucca and the esteemed Pontifical University of St. Thomas Aquinas in Rome, which ultimately led to his priestly ordination on May 28, 1904.