Born in Venice around 1494 to Alvise, procurator of St Mark, and Cecilia Giustinian. At the doge’s request, he was created cardinal deacon by Leo X in the great promotion of 10 July 1517.
During the sack of Rome in 1527 he remained in Castel Sant’Angelo beside Clement VII and after 26 November was handed over as a hostage to the Spaniards. He attended the coronation of Charles V at Bologna (1530). On 8 August 1524 he obtained the see of Padua, where he oversaw the rebuilding of the cathedral; then, on 27 January 1528, he also received that of Treviso. From 28 September 1526 until his death he likewise held the see of Emona in Istria on a more or less intermittent basis.
As first deacon he crowned Marcellus II and Paul IV and took part in eight conclaves. He was bishop of Ostia and Velletri from 12 May 1564 until his death in Rome on 29 June 1570, after fifty-three years as a cardinal.