Efforts to create Saikai National Park began in 1949, at the initiative of then-Sasebo mayor Masasuke Nagata.

The area encompassing the present park mostly fell within the territory of the former Sasebo Naval District of the Imperial Japanese Navy, and was regarded as a strategic zone in which photography was strictly prohibited, and visitation by outsiders was discouraged.

The Gotō Islands have interesting inlets and high cliffs as well as rare volcanic formations.

The park is valued for its scenic beauty and as an ecological support for the rich fishing grounds in the area.

The mild climate and warm currents result in semi-tropical vegetation, including tree ferns.