According to the 2021 census gazetteer files, Mona Township has a total area of 36.18 square miles (93.71 km2), all land.

As of the 2020 census[1] there were 267 people, 161 households, and 65 families residing in the township.

There were 130 housing units at an average density of 3.59 per square mile (1.39/km2).

The racial makeup of the township was 94.76% White, 0.37% African American, 0.00% Native American, 0.00% Asian, 0.00% Pacific Islander, 3.37% from other races, and 1.50% from two or more races.

37.90% of all households were made up of individuals, and 11.80% had someone living alone who was 65 years of age or older.