Twenty-one species of crinoids in six families are now known from the Marianas Islands, 17 species from Guam and 10 from the Commonwealth of the Northern Marianas Islands (CNMI). This paper adds nine previously unreported crinoid species each to Guam and the CNMI. The nomenclature of all 21 species is reviewed and updated following Rowe et al. (1986), Hoggett and Rowe (1986) and Messing (1995, 1998a). One apparently juvenile comasterid does not fit comfortably in any known genus and may represent a new taxon. A simple key to the shallow-water species of Guam is included. Crinoid faunal diversity on Guam is compared with that known elsewhere in the Indo-West Pacific.