
During the period of the Frankish occupation, the province of Kalavryta was the smallest administrative and tax unit of the theme of the Peloponnese. When Constantinople was captured by the Crusaders (1204) and the Principality of Achaia was established (1205), Kalavryta became the seat of one of its twenty baronies and was divided into twelve feudal knightly estates. The first baron was Othon de Turné, who was succeeded first by John and then by Godfrey. During this time, the city was named “Kalavryta,” and a castle was built (1208) to the east of the city, along with several smaller fortresses in the surrounding area.
In 1263, the Frankish barony was overthrown by the Greeks, who became the rulers of the region. Later, the de la Tremouille family, barons of Chalandritsa, became the lords of Kalavryta. Since 1257, they had been an independent barony, controlling a part of what had previously been the united barony of Patras. The second phase of Frankish rule lasted until 1330, when the Byzantine despots of Mystras, initially led by Cantacuzenus and later by the Palaiologos family, took control of the area. A portion of the Franks remained in the province of Kalavryta, converted to Orthodoxy, and Hellenized.
When Theodore I Palaiologos was defeated by the Turks, he leased Kalavryta to the Knights Hospitaller of Rhodes (1404). However, four years later, they were once again under the control of the Palaiologos family. In 1392, Theodore Palaiologos invited several families from Albania to bolster the Peloponnesian population, which had been decimated by the plague. From these families, two Albanian-speaking villages were founded in Kalavryta: Lykouria and Kgerbessi.
The Turks became the rulers of the area in 1460 after overcoming the strong resistance of the last commander of Kalavryta, Doxas.
The castle of Kalavryta, along with that of Salmeniko (1461), were the last two fortresses in the Peloponnese captured by the forces of Mehmed II the Conqueror.