The portunid crab Callinectes danae is abundant in Brazilian estuaries and coastal areas and is an important item to artisanal fisheries. This study investigated the distribution and population structure by sex and size, the size at sexual maturity, and sex-ratio of the species in Vitória Bay, Espírito Santo, southeastern Brazil. Crabs were collected monthly by nocturnal trawling during one year in six sampling stations distributed along an estuarine gradient and an independent depth gradient. Physico-chemical parameters of water were measured in situ on each station. A total of 3876 individuals were collected: 2537 females (1147 adults, 318 ovigerous, and 1072 juveniles), and 1339 males (444 adults and 895 juveniles). The mean carapace width (including lateral spines) at sexual maturity was 91.3 mm for males and 80.5 mm for females; the female-to-male sex ratio was 1.89∶1. Adult females occurred throughout the bay and year-round, but egg-bearing females were almost exclusively caught in deep and high salinity areas. Adult males and juveniles of both sexes occurred mainly in internal areas of the estuary, nearest river mouths; highest captures were registered in November. Both the scarcity of males, probably resulting from size-selective catch, and the low proportion of ovigerous females, compared with that observed in other Brazilian estuaries, suggest that the population has been overexploited.