His brief reign saw the loss of Venetian territory to Genoa and the Ottoman Empire, though Venice was to enjoy economic growth during this time.

Cornaro was instrumental in the discovery and suppression of the attempted coup d'état in 1355 by the then doge Marino Faliero, who intended to declare himself prince of Venice.

Following the dissolution of the plot and execution of the conspirators, Cornaro was briefly made vice-doge before a successor to Faliero could be appointed.

On the death of the previous incumbent Lorenzo Celsi on 18 July 1365, Cornaro was elected to the dogal office, despite the aspersions cast by his opponents over his advanced age, his wife's low birth and his friendships with foreign princes.

During the two and a half years of his reign, Venice saw no major changes or wars, although it lost the islands of Chios and Lesbos and the city of Phocaea to the Republic of Genoa.