It was during the turbulent period of the Albigensian Crusade that Castelnaud made its first appearance in the history books. At that time the castle belonged to a seignory of average importance, controlled by Bernard de Casnac, a fervent supporter of the Cathar faith and a man who was renowned for his cruelty. In 1214, the leader of the Albigensian crusade, Simon de Montfort, took the castle and installed a garrison there. Casnac fought back, re-taking the castle a year later and ordering that Montfort’s entire garrison be hanged. He was finally expelled from the castle by the Archbishop of Bordeaux, who burnt the castle to the ground.

After the Treaty of Paris, signed in 1259 between Saint Louis and Henry III in an attempt to put an end to the conflict between the Capetians and Plantagenets, the Périgord region was returned to the English; as a result Castelnaud came under English control. In 1273 the castle was returned to the legitimate feudal line, that of the Castelnaud, who paid homage to the Count of Périgord, a vassal of the King of France.

The end of the 13C saw the beginning of a period of prosperity and relative calm for Castelnaud. The castle soon became one of the main strongholds of the Périgord.

The conflict which became known as the Hundred Years War broke out in 1337. The English gained most ground in the first few decades of the war, after the Treaty of Brétigny-Calais granted them control of Aquitaine. In 1368, Magne de Castelnaud, the only heir of the Castelnaud family, married Nompar de Caumont; the Caumont family were to remain in possession of the castle until the French Revolution. During the Hundred Years War, the Caumont often fought on the side of the English.

In 1442, weary of English control of Castelnaud, the King of France ordered that the castle be placed under siege. The siege lasted three weeks, after which the English were finally driven away from the castle. In 1452 the Battle of Castillon brought the Hundred Years War to an end.

At the time of the French Revolution the lords of Caumont preferred the Château de Milandes to that of Castelnaud.

Castelnaud is now the most visited castle in the south of France.