Casselberry is a city in Seminole County, Florida, United States. The population was 26,241 at the 2010 census. The city is usually considered linked to the Orlando–Kissimmee–Sanford Metropolitan Statistical Area. According to the United States Census Bureau, the city has a total area of 7.1 square miles, of which 6.7 square miles is land and 0.4 square miles (6.06%) is water. Casselberry features over 30 lakes and ponds, the largest being Lake Howell, the Triplet Chain of Lakes, Lake Kathryn, and Lake Concord. The median home value in Casselberry is $105,300, with the national $184,700. The median rent is $1,039, with the national $949.