The reproductive biology of the red crab Pleuroncodes planipes, an abundant but unfished galatheid species, was studied using specimens collected from the west coast of Baja California, Mexico, in November 2006 and March 2007. Crabs were caught with a bottom trawl at predefined stations. Sex ratios were not significantly different from 1:1 (P > 0.05). The six stages of oogenesis and 10 oocyte substages in P. planipes are described. Results suggest a synchronous maturation pattern with multiple spawnings during the breeding season. In males, spermatogenesis occurs as a continuous process. The estimated cephalothorax length (CL) at 50% sexual maturity for females was 23.6 mm and 22.3 mm for the November 2006 and March 2007 cruises, respectively; for males, it was 26.8 mm and 25.3 mm. Batch fecundity of females ranged from 267 to 25,674 eggs for red crabs 9.5–33.87 mm CL. Batch fecundity was positively correlated with CL (P < 0.05; r² = 0.84 and 0.93).