He rose to prominence quickly, being repeatedly elected as ducal councillor, as a member of the Senate of Venice, and then serving as the Republic of Venice's ambassador to the Vatican, prior to serving as Procurator of St Mark's.

Following the death of his wife Lucia Barbarigo, Pesaro married his housekeeper, a low born woman whose brother was a criminal banished from the republic.

With the war against the Ottoman Empire at a low point, and many Venetian nobles considering giving up Crete, Pesaro gave an impassioned speech in the Maggior Consiglio (Grand Council) in favour of continuing the war, in the course of which he pledged 6000 ducats of his own money.

On April 8, 1658, Pesaro was elected as Doge on the first ballot, not least because he was considerably younger than his opponents, and it was hoped that he would have a longer reign than had his predecessors, a wish regrettably unfulfilled.

Pesaro was hated by the people of Venice, and fell ill soon after his election as Doge.