Kistler is a borough in Mifflin County, Pennsylvania, United States. The population was 292 at the 2020 census. Kistler is located at 40°22′50″N 77°52′4″W / 40.38056°N 77.86778°W. According to the United States Census Bureau, the borough has a total area of 0.3 square miles, of which 0.3 square miles is land and 0.04 square miles is water.