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 2006, the city had a population of 24,647. It is usually considered a suburb in the Greater Orlando area. Casselberry apartments for rent comparison page shows most up to date rent information on Casselberry apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.