An account of previous lists and descriptions of marine and freshwater harpacticoid copepods of Mexico yielded, by year 2010, 71 marine and 21 freshwater species from a variety of habitats. Sediment samples from the littoral zone to more than 2000 m depth along the Mexican Pacific coast, from the west coast of the Baja California peninsula, from the Gulf of Mexico, and from anchialine caves and cenotes from Yucatan, were taken during the last 15 yr as a continued effort to improve our knowledge of the diversity of the harpacticoid fauna from Mexico. This study shows that, at present, 151 species/subspecies distributed in 85 genera and 31 families are known from Mexican marine and freshwater systems. Additionally, a number of species belonging to 78 genera and 25 families are yet to be described. The checklist contains information on the locality, geographic coordinates, habitat, and source of the recorded taxa. There is a better knowledge of the harpacticoids from Sinaloa (northwestern Mexico). However, the number of species from Mexico is expected to grow rapidly in the forthcoming years.