He was the elder brother of Jean de Montluc. He served first as a private archer and man-at-arms in Italy, with Bayard for his captain, fought all through the wars of King Francis I of France, and was knighted at the battle of Ceresole (1544), to which victory he had brilliantly contributed as adviser to the young Duke of Enghien. Having apparently enjoyed no patronage, he was already middle-aged.
From then on, however, his merits were recognized.
His chief feat was the famous defence of Siena (1555) which he related himself. When the religious wars broke out in France, Montluc, a staunch royalist, held Guyenne for the king.
Henry III made him in 1574 marshal of France, an honour which he had earned by nearly half a century of service and by numerous wounds. He died at Estillac near Agen.