Montmorency was born at Chantilly to the ancient Montmorency family. His father had a senior status in the household of the king Louis XII. As a young boy he was brought up with the future King Francis I and they became close. In 1512, aged 19, Montmorency fought at the Battle of Ravenna, and in 1514 his sister Louise de Montmorency married Gaspard I de Coligny, and their children included the admiral of France.