Moriès-Castellet was born to the family of Françoise d’Arbaud de Châteauvieux and François de Cheylan du Castelet Moriès, from Fréjus. He was brother to Jean-Baptiste de Moriès de Castellet, and nephew to Jean-Baptiste de Glandevès du Castellet.
Moriès-Castellet joined the Navy as a Garde-Marine on 6 July 1735. He was promoted to Lieutenant on 23 May 1754.
In 1758, he was given command of the 26-gun frigate Oiseau. In September 1759, he captured the British merchantman Prince of Wales, and brought her back to Toulon. In 1760, he transferred to 32-gun Chimère, before returning to Oiseau from 1761 to 1762. He cruised off the coast of Spain and to Malta.
On 15 January 1762, he was promoted to Captain, and he took command of the 50-gun Fier.
On 19 March 1765, he married Cécile de Glandevès. In 1770, he served as flag captain on Provence, in a three-ship squadron under Rafélis de Broves that departed Toulon on 16 May, bound for Tunisia, where it blockaded the harbours of Sousse and Bizerte. Moriès-Castellet took part in the bombardment of the cities in late June.[10][11]
In 1774, he was given command of the 32-gun Atalante.
He was promoted to Chef d'escadre on 1 June 1778. That same year, he captained the 74-gun Hector in the squadron under Estaing. He took part in the Battle of Rhode Island, in the Battle of Grenada on 6 July 1779, and in the Siege of Savannah.