On 3 March 1625, Marco Giustiniani was appointed during the papacy of Pope Urban VIII as Bishop of Torcello.[1] On 27 October 1625, he was appointed during the papacy of Pope Urban VIII as Bishop of Ceneda.[1] On 7 April 1631, he was appointed during the papacy of Pope Urban VIII as Bishop of Verona.[1] He served as Bishop of Verona until his death on 23 April 1649.[1]