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.
Casselberry is located at 28°39′40″N 81°19′19″W.
According to the United States Census Bureau, the city has a total area of 7.1 square miles (18 km2), of which 6.7 square miles (17 km2) is land and 0.4 square miles (1.0 km2) (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.
Prior to European settlement in the 19th-century Native American groups inhabited the Seminole County area, including land in present-day Casselberry.
Casselberry was originally part of unincorporated Fern Park. Residents decided to incorporate Casselberry as a tax-free town in 1940, with the purpose of avoiding property taxes. The town was reincorporated as a city in 1965, and property taxes were reinstated in 1976.
At the 2010 U.S. Census, there were 26,241 people, 11,430 households, and 6,398 families residing in the city. The population density was 3,751.9 inhabitants per square mile (1,448.6/km²).