Females of the genus Cancer have a spermathecae whose connection with the ovary can be dorsal or ventral, depending on the species. The spermathecae is a structure specialized in receiving the spermatophores released by the male during mating. This study aims to describe and measure the reproductive structures of both sexes in the crab C. setosus. Females have a pair of ovaries in an H-type conformation; the anterior lobes are 2.4 times longer than the posterior lobes. The spermathecae has walls that are not extensible and a ventral-type connection with the oviduct, which indicates internal fertilization for this species. Sixty-four percent (64%) of the studied females presented a couple of spermatic blockages. In males, the first pair of pleopods is tubular, with the distal tips pointed and/or open, forming a fold. The second pair of pleopods ends in a funnel structure with 12 side extensions. The two testes are whitish in color and converge in a vas deference (VD) that has three zones: proximal, middle, and posterior. Each of these plays a role in the elaboration of the spermatophores and seminal fluid production.