The minor district (king amphoe) Kranuan was established on 1 January 1948 by splitting it from Nam Phong district. It was upgraded to a full district on 22 July 1958.
The district is divided into nine subdistricts (tambons), which are further subdivided into 81 villages (mubans). Nong Ko is a township (thesaban tambon) which covers parts of tambon Nong Ko. There are a further nine tambon administrative organizations (TAO).