The former fortress was put up by Foulques Nerra, count of Anjou, in the 11th century. He gave it to one of his loyal lieutenants, Berlay... this lord gave its name to the little city which became Bellay.
This family raised a surrounding wall in the 13th century then the castle fell to the Melun family, when Agnès Bellay married Guillaume of Melun in 1217. The Melun owned the fief for two centuries and rebuilt the wall, separated from the town by a ditch. Then Montreuil fell to the Harcourt family in 1415.
Guillaume d'Harcourt rebuilt the small castle, the master's office dwelling, the Gothic collegiate church and the residential buildings. He also raised the New castle, flanked by 4 round towers. Right in front of this castle, the Small castle, also called Canons' dwelling, which housed steamed rooms, fit in the 15th century by the Harcourt family. A pretty modern castle...
In 1488, the last member of this family passed away, so the castle fell to the Longueville, Guillaume d'Harcourt's descendants. Then for the first time in its long story, Montreuil was sold in 1662 to the marshal de La Melleraye then to the Trémoille. One of the owners transformed it into a kind of barn and demolished the keep.
The Trémoille succeeded in getting back their castle... but Montreuil was damaged... the restoration was too expensive for the family, so they sold it in 1822... The new owners asked a disciple of Viollet-le-Duc to restore the place in 1860.