Population demography studies provide a vital insight into the status of wildlife populations, especially for long-lived and at-risk populations such as many turtles. The present study investigated the population demography and habitat association of a southwest Florida barrier island population of Terrapene bauri (Florida Box Turtle). We used mark–recapture methods to estimate population size, sex ratios, and age and size distributions along with habitat association. Total population size was estimated to be 4014 turtles for the island, with an adult to juvenile ratio of 3.4:1.0 and an adult male to female sex ratio of 1.2:1.0. Turtle body size was noticeably larger than that for other insular populations of Florida Box Turtle. Turtles were found to be larger in the central and west end of the island when compared to the more developed east end. Juveniles were found to be more likely associated with dune habitat, and adults more likely associated with golf course and hardwood hammock habitats. This study establishes baseline data for a potential at-risk Florida Box Turtle population and provides findings that can contribute to future conservation of the species.