Jean de Quélennec, viscount of Faou, owned Bienassis in the 15th century and gave it to his son Geoffroy, who probably raised the castle in 1415.
Françoise de Quélennec inherited the estate and gave it to his second husband, Gilles Visdelou, lord of La Goublaye, in 1592: this one completely restored the castle. But Visdelou opted for Protestants during the war of Religion... a very bad choice! Captains Chefdorge and Vieuxville-Villevolette besieged the place, plundered it, and exiled Visdelou from his estate for... 10 long years!
Gilles Visdelou was exiled in the fort La Latte ("Castle La Latte"), which belonged to his family... anyway, in 1620, he rebuilt the surrounding wall of Bienassis. Claude Visdelou inherited the place when his father died in 1626... and the family died out in 1715: the castle fell to the La Marck family, then to the general de Valletaux in 1795.