[3] Another uncle, Cardinal Antonio's brother Teodoro, was Governor of La Palice, of Genoa (from 1526), of Milan, and a Marshal of France.

Pietro and Paolo at Lodi Vecchio, and Abbot Commendatory of the Cistercian house of Aquafredda (Santa Maria Montisfrigidi) on Lake Como.

He was Chamberlain of Honor to Pope Julius II (1503–1513), and then Protonotary Apostolic de numero Participantium,[7] a title he still held when appointed Cardinal.

[8] But when Julius II allied himself with Venice and Spain against France in 1511, Trivulzio left the Papal Court and returned to Milan.

The election of Pope Leo X (Medici) in 1513, however, changed the political scene, and Trivulzio returned to court.

The Conclave to elect his successor should have begun in mid-December, but the Cardinals themselves fixed an opening date of 18 December.

When it was learned, however, that the Cardinal of Ivrea, Bonifacio Ferrero, had been detained by Spanish troops at Pavia, the decision was taken to postpone the opening of the Conclave until 26 December.

It was not until 9 January 1522, after the tenth ballot had taken place, that a successful election was achieved, once it was revealed that the Emperor Charles V favored his Regent in Spain, Cardinal Adrian Dedel, Bishop of Tortosa.

The Conclave to elect his successor held its opening ceremonies on Thursday 1 October 1523 with thirty-five cardinals in attendance.

[21] He was named Administrator of the diocese of Avranches on 2 May 1526, and he relinquished the post on 19 October 1526 to Jean de Lagniac, a member of the King's Council.

[22] In 1524-1525 Cardinal Trivulzio built a villa to the east of Rome, near the source of the Aqua Adria, at Sulmone.

[27] The Pope finally left the Castel on 6 December 1527 after seven months in captivity, and immediately headed for Capranica, on his way to Orvieto.

In September 1533 Pope Clement VII made a journey to Marseille, having arranged a marriage between his niece Catherine and the second son of King Francis, Henri, Duc d' Anjou.

The marriage took place on 28 October in Marseille, but the peace talks, in which the Pope met repeatedly but separately with the two monarchs, produced no resolution of any of the issues.

In August 1534, Cardinal Trivulzio, who was keeping King Francis I informed about French business in the Roman Curia, wrote that the Pope was suffering from a serious illness and that the doctors believed he was in danger of death.

The Conclave to elect his successor began on the evening of 10 October, with thirty-two cardinals in attendance at the opening ceremonies, one of whom was Agostino Trivulzio.

[40] Trivulzio received his credentials as Legate on 14 June; he had an interview with the Emperor at Savigliano, south of Turin, on 9 July.