Kermadec was born to the family of Anne François du Mesacm de Mescaradec and of Jean Guillaume Huon de Kermadec.
Kermadec joined the Navy as a Garde-Marine on 12 January 1766.
[2] Serving on the 74-gun Annibal, in the division under Suffren, Kermadec took part in the Battle of Porto Praya.
He was wounded by a bullet to the thigh, but refused to receive medical attention before the fighting was over.
[1] Later, he was given command of the 24-gun corvette Subtile and took part in the Battle of Negapatam on 6 July 1782.