Ambassador to Rome

At some point in 1513, Castiglione was nominated by Francesco Maria Della Rovere as his ambassador and orator in Rome, with power of attorney, from May 1514, to act in civil, penal matters and connected matters, with the authority of the Duke of Urbino, prefect of Rome and Captain General of the armies of the Church. Thus Baldassarre also got involved in complex dealings with the Church administration and the Camera Apostolica for the resolution of debts contracted Francesco Maria. Meanwhile, from Mantua, his mother administered his estate and castle in Novilara, aided locally by Girolamo Tirabosco, her  master of the house.

Castiglione lived in an environment frequented by people who were the protagonists of great international diplomacy, mindful and knowledgeable of the Italian and European situation, and who cultivated the arts and letters. They combined the cult of neo-Latin poetry and antique erudition with the celebration of the glories and splendours of the new Rome of the popes. In particular he tied himself to the group of friends of Hans Goritz, the gentleman, originating from Luxemburg, whom Leone X nominated apostolic proto-notary and master of pleas. He writes about this in the lyrical poem Cleopatra, dedicated to a famous marble statue (an ancient copy of an original from the Hellenic era) that in 1512 Giulio II had bought for the courtyard in Belvedere.

In 1514 he witnessed the spectacular entry into the city of the elephant Annone, that the sovereign of Portugal, Don Manuel I, had sent from India as a gift for the Pope, following the fashion of the time for exotic things, to solicit assistance in his war against the Saracens and to obtain recognition of Portuguese conquests in Asia and America. He also met, for the first time, Miguel da Silva, who had established himself in Rome at the end of 1514, as ambassador and agent of the King of Portugal to the Pope.