what county is casselberry fl in
Homefacts City Report. Casselberry is located in Seminole County, FL. The population is 26,360, making Casselberry the 5th largest city in Seminole County. There are 4 public schools in Casselberry with an average Homefacts rating of A-. The total crime rate for Casselberry is moderate, and there are 37 registered sex offenders residing in the city.