Two co-occurring species of the copepod genus Karllangia were found in the beach slope of Manzanillo, Caribbean coast of Costa Rica. Until now, the taxon has comprised three species from the Red Sea (K. arenicola arenicola Noodt, 1964), North Andaman and Car Nicobar Island (K. arenicola bengalensis Wells and Rao, 1987), Inhaca Island of Mozambique (K. psammophila Wells, 1967), and South Africa (K. tertia Kunz, 1975). The discovery in Costa Rica suggests a circumtropical-subtropical distribution of Karllangia. The characteristic sexual dimorphism of the 2nd antennae is interpreted as a significant synapomorphy of both new Costa Rican species (K. pulchra and K. obscura), which together with K. psammophila and K. a. bengalensis, probably constitute a monophyletic subgroup.