The location of Saga Castle was originally a fortified village under the control of the Ryūzōji clan, warlords of a small area of northern Kyūshū in the Muromachi period.

After Ryūzōji Takanobu was defeated by a coalition of Shimazu and Arima forces in 1584, his retainer Nabeshima Naoshige gained control of the castle.

Naoshige allied the clan with Toyotomi Hideyoshi and gained personal distinction during the Japanese invasions of Korea, during which time he befriended noted castle architect Katō Kiyomasa and future Shōgun Tokugawa Ieyasu.

The palace portion was restored two years later in the outer bailey, which was the centre of the Saga domain government for most of the Edo period.

Another fire occurred in 1835, after which the buildings were reconstructed by Saga domain’s final daimyō Nabeshima Naomasa.