According to the 2021 census gazetteer files, Fountain Creek Township has a total area of 36.23 square miles (93.84 km2), all land.

A Union Pacific rail line connecting Chicago and St. Louis runs northeast-to-southwest through the eastern half of the township, and a branch of the defunct Chicago and Eastern Illinois Railroad crosses it near the northern border.

The township contains one cemetery: Old Apostolic, near Fountain Creek.

As of the 2020 census[1] there were 315 people, 112 households, and 79 families residing in the township.

24.10% of all households were made up of individuals, and 17.90% had someone living alone who was 65 years of age or older.