The castle, located on top of the mountain, was built in 1184 by one of the generals Caladina to protect the iron mines of Ajloun and protection against attacks by the Franks. Ajloun Castle dominated the three main routes leading to the Jordan valley and protected the trade routes between Jordan and Syria. He was an important link in the chain of fortifications designed to protect against the Crusaders, who for decades tried unsuccessfully to capture the castle and the nearby village.

Originally the castle had four towers with battlements thick walls loopholes for archers, and was surrounded by a moat and a depth of 16 to 15 meters.

In 1215, the Mamluk governor of Aibak ibn Abdullah expanded the castle, adding yet another tower at the southeast corner and erecting a bridge, decorated with figures of pigeons, which can be seen today.

In the XII century. Castle was commissioned governor of Aleppo and Damascus Salah ad-Din Yusuf ibn Ayyub. When it was restored the northeastern tower. In 1260, work on the reconstruction of the castle was interrupted and he fell to the Mongols. Soon, however, the Mamluk Sultan Baybars reconquered and rebuilt the fortress it again.