The aim of the present study was to characterize the total and seasonal fecundity of the hermit crab Paguristes tortugae as well as the influence of shell type on fecundity using the morphometric relationship. Ovigerous females were collected monthly from January to December, 1998, in the infralittoral region of Anchieta Island. Samplings were performed using SCUBA. The hermit crabs and the gastropod shells were measured. Hermit wet weight and shell dry weight were recorded. For the fecundity analysis, only ovigerous females with the eggs in the early phase of development were selected. The number of eggs carried by individuals of several sizes (shield length), condition of development, and egg size were determined. A high percentage (69.88%) of ovigerous females with eggs in the early phase of development were captured, with a low frequency (4.29%) of females with eggs in the final stage of development. Size-frequency distribution during the months showed two peaks in the ovigerous female population (2.5 to 3.4 mm and 4.0 to 5.4 mm of SL). Mean ± SD fecundity was 132 ± 102 eggs and tended to increase with increasing SL. No significant difference in fecundity occurred among the various seasons of the year. The results showed continuous and elevated reproduction of P. tortugae, with a high reproductive potential for the population. The pattern of the frequency distribution of ovigerous females tending to bimodality may be characteristic of a population with a two-year life cycle. Considering the four shells most occupied by P. tortugae (Pisania auritula, Cerithium atratum, Morula nodulosa, and Leucozonia nassa), the highest fecundity was observed for ovigerous females occupying larger shells (P. auritula and L. nassa). The reproductive aspects of P. tortugae were related to strategies developed to compensate for interspecific competition, i.e., high and continuous reproductive effort, early maturity, low fecundity, and larger eggs produced.