As a result of the parasitological examination of the crabs, Uca uruguayensis (Ocypodidae) and Chasmagnathus granulatus (Varunidae), third-stage larval nematodes belonging to the family Acuariidae and to the genus Ascarophis were found in the crabs' hemocoel, both free and embedded in host tissues. Larval nematodes are described and illustrated here. The presence of these larval nematodes in both crab species may be influenced by the similarity in the crabs' habitat and feeding behavior. Both species of burrowing crabs inhabit the upper intertidal zones and feed on sediments, and consequently, they have similar chances of coming into contact with eggs and infective larval nematodes deposited in the feces of birds and fish definitive hosts. Since the life cycles of the larval nematodes from U. uruguayensis and C. granulatus remain unknown and because the adult stage is undescribed, they cannot be assigned to a given genus or species. The validity of a previous record of Skrjabinoclava sp. in U. uruguayensis from Bahía Samborombóm is also discussed.