Casselberry, FL has a population of 26,649 and is the 1,620th largest city in the United States. The population density is 3,853 per sq mi which is 1212% higher than the Florida average and 4152% higher than the national average. The median age in Casselberry is 39 which is approximately 7% lower than the Florida average of 42. In Casselberry, 48% of the population over 15 years of age are married, 73% speak English and 21% speak Spanish. 40% of Casselberry residents were born in Florida, 41% were born out of state, 8% were born outside of the United States and 11% were foreign born.