He served as podestà of various towns in Venice's Terraferma, and as Venetian Ambassador to the Vatican during the pontificate of Pope Alexander VII.

During Valier's reign, the Most Serene Republic proposed terms for ending the Cretan War, but these were rejected by the Ottoman Empire.

Valier ordered a Venetian fleet to sail through the Dardanelles to attack Istanbul, in the hopes that this would at least relieve the pressure on the Siege of Candia; this expedition had only limited success.

Desperate for money with which to fund the war, in 1655, Valier allowed the Jesuits, who had been expelled from the Venetian Republic by Leonardo Donato in 1606, to return in exchange for a cash payment.

He was interred in the Basilica di San Giovanni e Paolo, a traditional burial place of the doges.