Overharvesting of the land crab Cardisoma guanhumi (Latreille, 1828) has occurred in some locations including Puerto Rico. We placed passive integrated transponder (PIT) tags in this crab, C. guanhumi, to estimate a population on the southern coast of Vieques island, Puerto Rico. We were able to recapture marked animals approximately 1 year after tagging. We estimated the population of C. guanhumi on the southern central coast Vieques to be approximately 29 000 individuals. The recapture locations of individuals averaged 136 m (SE ± 55.1) from their point of initial capture. This is remarkable because these crabs are reported to move annually inland up to several kilometers for mating. Either some C. guanhumi do not move during mating season, or they return to the same location they left. The carapace size of captured C. guanhumi suggests hunting was not greatly pressuring populations at the time of this study. These findings may help natural resource managers implement a conservation plan that will allow sustainable harvest of this population.