As a young man, he joined the Knights Hospitaller, becoming Grand Prior of Cyprus, an office he later resigned in favor of his younger brother Federico Cornaro.[1]
Under Pope Pius IV, he headed the commission charged with dealing with the riots fomented by the Carafas during the pontificate of Paul IV.[1] He was named administrator of the see of Bergamo on 13 March 1560.[1] He resigned the administration of Bergamo in favor of his nephew Federico on 15 January 1561, at which time he became administrator of the see of Trogir.[1] He resigned that post on 18 April 1567.[1] On 26 February 1561 he opted for the order of cardinal priests, and on 21 June 1564 received the titular church of San Marco.[1]