Between 1316 and 1320 Gui acted as Procurator General of the Dominican Order, representing its interests within Pope John XXII's court at Avignon, and during this time he also undertook diplomatic missions on behalf of the papacy. In January 1317, accompanied by the Franciscan Bertrand de la Tour, he was sent on a papal mission to Italy to instigate peace negotiations between the cities of northern Italy and Tuscany. Following their return to Avignon early in 1318, the two were sent to Flanders to mediate in the conflict between King Philip V of France and the Count of Flanders, Robert III. Both efforts were ultimately unsuccessful. Pierre Gui's hagiography claims that while in Avignon Gui also performed two miracles, curing the inquisitor of Barcelona, Arnaldus Borgueti's insomnia and the friar Guillermus de Gardaga's fever and dysentery.