According to the United States Census Bureau, the township has a total area of 35.8 square miles (92.7 km2), all land.

The main geographic feature of Lismore Township is the Elk Creek, which flows westward and eventually joins the Big Sioux River system.

(A separate and distinct Elk Creek exists elsewhere in Nobles County and flows eastward, joining the Des Moines River system.)

Main highways include: Organization of Lismore Township was approved by the Nobles County Board on July 21, 1880.

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