Joseph was very old and ill and died on 10 June 1439. His death caused much grief to all present at the council, as he was a fervent supporter of union between the Churches; before his death, he drew up and signed an important pro-union declaration for the council. His grave in the Dominicanconvent church of Santa Maria Novella in Florence survives, with an elaborate fresco portrait in a semi-Byzantine style. He was succeeded as Patriarch of Constantinople by Metrophanes II, who was appointed by Emperor John VIII on account of his similarly pro-unionist sentiments.