The ectoparasitic harpacticoid copepod, Balaenophilus manatorum (Ortíz, Lalana and Torres, 1992) (syn. Balaenophilus umigamecolus Ogawa, Matsuzaki and Misaki, 1997), has been reported on 3 species of marine turtles from the Pacific and the Mediterranean and from the West Indian manatee off Cuba in the Caribbean. The 3 available descriptions of this species were made using light microscopy. In this paper, we provide an amended description of B. manatorum using scanning electronic microscopy (SEM) for specimens in the collection from which B. umigamecolus was originally described. This material was collected from 1 loggerhead sea turtle, Caretta caretta, from Japan. The use of SEM allowed us to add several new microcharacters to the original description but, more importantly, allowed us to correct a number of the traits originally described. Some of the corrections could affect the interpretation of putative homology and variability of characters among populations of B. manatorum. A SEM comparison of specimens of B. manatorum from loggerheads from Japan and the western Mediterranean suggested the existence of morphological stasis between these populations. However, there were apparent meristic differences with a recently published description of this species from olive ridleys, Lepidochelys olivacea, in Mexico. Although B. manatorum is currently considered as a single, widespread taxon, the possibility that it actually represents a species complex deserves further attention.