According to the United States Census Bureau, the township has a total area of 36.0 square miles (93 km2), all land.

The Buffalo Ridge, the drainage divide between the Mississippi and Missouri Rivers systems, extends through Dewald Township.

Dewald Township is located in Minnesota's 1st congressional district, represented by Mankato educator Tim Walz, a Democrat.

At the state level, Dewald Township is located in Senate District 22, represented by Republican Doug Magnus, and in House District 22A, represented by Republican Joe Schomacker.

Dewald Township is represented by Nobles County Commissioner Matt Widboom.