Learedius learedi Price, 1934, is redescribed using specimens obtained from the hearts of 3 black turtles, Chelonia mydas agassizii, from Magdalena Bay, Baja California Sur, Mexico. The redescription is consistent with the original description but provides an unreported range of variation in testes shape and position and adds new information about the reproductive systems, such as the presence of a papilla in the pore of Laurer's Canal and the presence of an external seminal vesicle instead of a preovarian seminal receptacle. Of 4 turtle hearts examined, only 1 was free of parasites (75% prevalence). In all, 128 parasites were found, a mean intensity of 43 worms per heart. This is the first record of the occurrence of L. learedi in C. m. agassizii in Mexico, expanding the known range of the parasite to the Baja California Peninsula.