As of the census[1] of 2000, there were 348 people, 151 households, and 120 families residing in the township.

14.6% of all households were made up of individuals, and 4.6% had someone living alone who was 65 years of age or older.

About 5.0% of families and 3.0% of the population were below the poverty line, including none of those under the age of eighteen or sixty-five or over.

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

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