The minor district (king amphoe) Tan Sum was created on 18 September 1978, when the three tambons  Tan Sum, Samrong, and Chik Thoeng were split off from Phibun Mangsahan district.
On September 18, 1978, the minor district (king amphoe) Tan Sum was formed by splitting off the tambons Tan Sum, Samrong, and Chik Thoeng from Phibun Mangsahan district.