He was Bishop of Ivrea from his election on July 28, 1497 until November 5, 1509, when he resigned in favour of his brother Gianstefano. On November 5, 1509, the day he resigned as Bishop of Ivrea, he was transferred to the see of Vercelli; he later resigned this office on September 17, 1511 in favor of his brother Agostino Ferrero. At that time, he returned to the see of Ivrea, occupying this see until May 17, 1518, when he resigned in favor of his nephew, Filiberto Ferrero.
From 1499 to 1519, Bishop Ferrero was also the Prior of San Pietro di Chambéry. He was administrator of the see of Nice 1501-04. In 1504, he beame prior of Santi Giovanni e Sebastiano di Benna, a post he held until 1542. He was a participant in the Fifth Council of the Lateran.
He opted for the suburbicarian see of Sabina on February 26, 1535. He was Prior of San Egidio di Verrès from 1535 on. He was briefly administrator of Vercelli upon the death of his brother Agostino, from September 1 to December 20, 1536, at which time he resigned in favor of his nephew Pietro Ferrero. He was dean of the Chapel of Santissima Sindone di Chambéry from June 4, 1537.
On November 28, 1537, he opted for the suburbicarian see of Porto e Santa Rufina. At this time, he became Sub-Dean of the College of Cardinals. He was also provost of the chapter of the collegiate church of San Gervasio di Ginevra from 1537; provost of San Bernardo di Montjovet from 1537; and prior of San Pietro di Nantua from 1537. In 1540, he was papal legate to Bologna. He was also prior of San Stefano di Robbio until 1542.