This study provides descriptive information on the natural history and life history of an invasive population of Charybdis hellerii, which is native to the Indo-West Pacific region, and which invaded the western Atlantic Ocean in the late 1980s. In this study, sampling at 27 sites along the Indian River Lagoon, Florida, during 1995–1999 showed that this crab is established in structured habitats (riprap of jetties, coralline ledges, mangrove roots, and dense algae) near inlets of the central and southern portions of the lagoon. It was not found at sites away from inlets, nor from apparently suitable structured habitats at an inlet to the north of Cape Canaveral. Although crab abundances were low, the broad size structure of the population indicates sustained recruitment into the population. Data on life history features and formal larval descriptions were derived from a cohort of larvae reared in the laboratory, including egg incubation and hatching, complete larval development, early crab instars, juvenile growth to sexual maturity, and brood production. Larval descriptions include detailed drawings of all apendages, as well as the carapaces, abdomens, and telsons for all 6 zoeal stages, and a photograph of the megalopa. Charybdis hellerii possesses numerous life history traits and natural history characteristics that are adaptive for invasion of new geographic regions, including: (1) a relatively long larval life (44 days), which facilitates dispersal; (2) rapid growth and maturation within about one year, contributing to a short generation time, which promotes rapid population growth; (3) the ability to store sperm and to produce multiple broods of high fecundity in rapid succession, which favors rapid expansion of founder populations; (4) generalized carnivorous diet, which allows opportunistic exploitation of a variety of food resources; (5) ability to use a diversity of structured habitats, which provides opportunity to exploit a range of habitats, but also suggests that its secretive or cryptic behavior may serve to protect it from visual predators.