Fifty-two ovigerous females of Cancer johngarthi were caught from the Baja California Peninsula's western coast, Mexico. Carapace length, carapace width and total weight of each specimen were registered. Fecundity estimates were obtained from the wet weight of eggs in each organism. Mean fecundity was 765,227 eggs, corresponding to a mean carapace width of 117 mm, and the mean relative fecundity was 4,305 eggs per gram of female body weight. Fecundity data (F) were fitted in relation to carapace width (CW) to the power model F = 0.84CW^2.87, R² = 0.52. C. johngarthi has a high population renewal capacity compared with other larger species like Maiopsis panamensis, which produces between 351,000 and 1,162,668 eggs, and Stenocionops ovata, which produces between 35,187 and 180,057 eggs; in both species, the relative fecundity is lower than 1,000 eggs per gram of female body weight.