Nematodes are among the most common parasites in aquatic mammals. Because of their cuticular covering, these worms are frequently collected from the examination of feces or stranded hosts. This work provides new records of three nematode taxa infecting three different aquatic mammal species (Lontra longicaudis annectens, Trichechus manatus, and Zalophus californianus) in Mexico. Additionally, it brings together all available published records about this country's nematode fauna parasitizing aquatic mammals. The aim is to describe the current state of the art, which sets the basis for the strategic design of future research. Given the diversity of printed sources recording nematode fauna, we gathered literature, including theses and articles in journals profiled in the Journal Citation Reports or similar academic databases. The compiled information shows that 24 nominal nematode taxa have been reported from 11 species of aquatic mammals in Mexico. Our study exhibits irregular patterns of geographic distribution and host spectrum, existing entire marine ecoregions, and numerous host species lacking records.