The minor district (king amphoe) Sanom was established on 1 July 1971, when the five tambons Sanom, Khaen, Na Nuan, Nong Rakhang, and Phon Ko were split off from Rattanaburi District.
The smaller administrative division (king amphoe) Sanom was established on 1 July 1971, when the five tambon units—Sanon, Khaen, Na Nuan, Nong Rakhang, and Phon Ko—were detached from Rattanaburi District.