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 founded on 1 July 1971, when five tambons—Sanon, Khaen, Na Nuan, Nong Rakhang, and Phon Ko—were separated from Rattanaburi District.