[1] According to the 2021 census gazetteer files, Andover Township has a total area of 36.56 square miles (94.69 km2), all land.

As of the 2020 census[3] there were 881 people, 264 households, and 214 families residing in the township.

There were 399 housing units at an average density of 10.91 per square mile (4.21/km2).

The racial makeup of the township was 95.01% White, 0.00% African American, 0.23% Native American, 0.00% Asian, 0.00% Pacific Islander, 0.68% from other races, and 4.09% from two or more races.

17.00% of all households were made up of individuals, and 8.30% had someone living alone who was 65 years of age or older.