It was in the troubled context of the Crusade against the Albigensians that Castelnaud made its appearance in history. The castle was at the head of a domain of middling importance; to the north, the Dordogne River marked the boarder with the lands of the powerful barons of Beynac. The master of the domain was Bernard de Casnac, ardent defender of the Cathar faith with a reputation for cruelty. In 1214, the leader of the Albigensian Crusade, Simon de Montfort, took the castle and installed a garrison there. But, Casnac fought back and succeeded in retaking the castle one year later.
He hanged Montfort's entire garrison before being definitively driven out himself by the Archbishop of Bordeaux who subsequently burned the castle.