This paper aims to study the morphological and gonadal maturity of the swimming crab Callinectes danae in the Santa Cruz Channel, Brazil. Crabs of both sexes were measured at carapace width (CW), carapace length (CL), abdomen width (AW), length of the right chelipod (LRC), and dissected to visualize the gonads. The gonadal maturity was estimated based on the frequency of mature individuals per class of CW, and the determination of morphological maturity was based on the relationship between the structures LRC versus CW for males and AW versus CW for females. The sizes that 50% of females reached gonadal and morphological maturity were 62.5 and 59.5 mm CW respectively. In turn, the sizes that 50% of males reached gonadal and morphological maturity were 74.5 and 70.5 mm CW respectively. In the analysis of dispersion of points in relation to AW versus CW, it could be observed that juvenile females showed positive allometry and adult females showed negative allometry, indicating a higher growth rate during the juvenile phase, related to the need of expanding the abdomen for egg incubation at the adult phase. In the relation LRC versus CW, it was observed that both juvenile and adult males showed positive allometry, but changes in the degree of allometry were evident between the two phases. The exceeding growth of the chelipod of males may be related to the reproductive process, including courtship and agonistic interactions with other males.