A taxonomic reappraisal of the marine littoral Cafius algarum (Sharp, 1874) and its related species along the western Pacific and the western Atlantic coasts including the Caribbean Sea is presented based on morphological and molecular characters (COI and 28S). Specimens of the three species (C. algarum, Cafius subtilis Cameron, 1922, and Cafius aguayoi Bierig, 1934), each having its own distinct geographic distribution, are extremely similar to each other including the form of the aedeagus. The molecular analyses support the validity of C. algarum with two synonymies based on morphological characters. Genetic divergence of COI using uncorrected p-distance among the three Cafius Stephens species ranged from 0% to 5.27%. All three species were strongly supported as a single lineage on both neighbor-joining and parsimony trees. Cafius subtilis, new synonym and C. aguayoi, new synonym are synonymized under C. algarum. Cafius algarum is redescribed with illustrations of diagnostic characters. The distributional extension among the populations of C. algarum is briefly discussed.