Casselberry is a city in Seminole County, Florida, United States. The population was 22,629 at the 2000 census. According to the U.S Census estimates of 2009, the city had a population of 24,792. It is usually considered a suburb in the Orlando–Kissimmee-Sanford Metropolitan Statistical Area. Casselberry is located at 28°39′37″N 81°19′24″W / 28.660275°N 81.323264°W / 28.660275; -81.323264. According to the United States Census Bureau, the city has a total area of 7.1 square miles (18.4 km²). 6.7 square miles (17.2 km²) of it is land and 0.4 square miles (1.1 km²) of it (6.06%) is water.