Waseca County is a county located in the U.S. state of Minnesota. As of 2010, the population was 19,136. Its county seat is Waseca.
According to the U.S. Census Bureau, the county has a total area of 433 square miles (1,121 kmē), of which 423 square miles (1,096 kmē) is land and 10 square miles (25 kmē) (2.21%) is water. The Le Sueur River flows through a part of the county.