Alessandro was given a humanist education at the University of Pisa and the court of Lorenzo de' Medici. Initially trained as an apostolic notary, he joined the Roman Curia in 1491 and in 1493 Pope Alexander VI appointed him Cardinal-Deacon of "Santi Cosma e Damiano". Farnese's sister, Giulia, was reputedly a mistress of Alexander VI, and might have been instrumental in securing this appointment for her brother. For this reason, he was sometimes mockingly referred to as the "Borgia brother-in-law," just as Giulia was mocked as "the Bride of Christ."