Previously nine species belonging to the crustacean order Tanaidacea have been described from Hawaiian waters. Specimens of a new metapseudid tanaidacean, Cryptapseudes leroyi David & Heard, n. sp., from the western Main Hawaiian Islands were discovered in collections of the Bernice P. Bishop Museum. The new species, which represents the fourth member of the genus Cryptapseudes Băcescu, is distinguished from the other three members of the genus by a combination of characters including an antennule with the outer flagellum having three or four articles (no more than two reported for other known species) and article-3 of the mandibular palp with seven to eight finely pectinate setae. An artificial key is presented to distinguish the four species. Discovery of C. leroyi in Hawaiian waters extends the range for the genus from the western Indian Ocean over 14,000 km northeast to the tropical waters of the midnorthern Pacific Ocean.