Arendahl Township was organized in 1860, and named after Arendal, in Norway.

As of the census[1] of 2000, there were 333 people, 118 households, and 94 families residing in the township.

The racial makeup of the township was 99.70% White and 0.30% Native American.

There were 118 households, out of which 34.7% had children under the age of 18 living with them, 71.2% were married couples living together, 2.5% had a female householder with no husband present, and 20.3% were non-families.

15.3% of all households were made up of individuals, and 5.9% had someone living alone who was 65 years of age or older.