In 1513 he was admitted to the household of Cardinal Giulio de' Medici, and advanced so rapidly in Latin and Greek that he soon became an eminent member of the Academia Romana.
He led a severely religious life, and was a member of the Oratory of Divine Love (Sodalitium Divini Amoris) of St. Cajetan and Cardinal Carafa (future pope Paul IV).
After his ordination to the priesthood, and the death of Leo X, he was sent by Cardinal Giulio, his patron, on a mission to Charles V, and returned to Rome with the new pope, Adrian VI.
Giberti was chosen a member of the Consilium de Emendanda Ecclesia, the reform committee decreed by Paul III, but political events soon put an end to these labours.
His complete works were edited by the scholars Girolamo and Pietro Ballerini (Constitutiones Gibertinae, Costituzioni per le Monache, Monitiones generales, Edicta Selecta, Lettere Scelte, 1733, 1740), together with an appendix containing the story of his life, a Dissertatio de restitutâ ante concilium Tridentinum per Jo.