Growth curves of the geoduck Panopea globosa were compared from four zones in northwestern Mexico, with three zones in the Gulf of California (Guaymas, Puerto Peñasco, and San Felipe) and one zone on the Pacific Coast of the southern Baja California Peninsula (Bahía Magdalena). The curves were shaped using the von Bertalanffy growth model. The lengths-at-age data for each location were obtained from fishery-independent data at each location. The average asymptotic lengths of P. globosa were 114.4, 156.6, 161.5, and 168.4 mm in Guaymas, Puerto Peñasco, San Felipe, and Bahía Magdalena, respectively. The Kimura's likelihood ratio test was used as the goodness-of-fit trial. In comparison with geoducks from the other locations, geoducks from Guaymas, located on the central Gulf of California, were the shortest, with a significant difference in length from those at the other three sites. Geoducks from the upper Gulf of California (Puerto Peñasco and San Felipe) and Pacific Coast had no significant differences among them. Because the fishing management strategy for this species uses the minimum legal size (MLS), the MLS should vary regionally to promote sustainable use.