The fortress is composed of a walled enclosure, which houses the heart of the population and the castle proper, and of five exterior towers, separate and strategically placed.

In 1184, Fernán Martínez de Ceballos, military captain under Alfonso VIII of Castile, besieged the fortress for nine months before finally capturing it in the name of his king.

From then on, the Castle of Alarcón received much attention from the successive kings of Castile, who expanded and reinforced it while providing it with its own charter (fuero) and granting it lordship over extensive neighboring territories.

Spanish historian Andrés Marcos Burriel writes that its domain comprised 63 villages, including Albacete, La Roda, Villarrobledo, Castillo de Garcimuñoz, Belmonte and many others.

Juan and his son Diego López Pacheco [es] sided with Joanna of Castile, a claimant to the throne, against Queen Isabella and her husband King Ferdinand.

In 1963, the Minister for Information and Tourism, Manuel Fraga Iribarne, expropriated it from the family of Álvarez Torrijos Torres, native of La Almarcha but with paternal ancestors from Gascas.

The legend of the Castle of Alarcón tells the story of how the stone blocks in the encircling wall were stained with blood, represented today by curious black and reddish spots on the mortar.