The islands and islets of Bahía de Chamela, in the Eastern Tropical Pacific, were declared as the first marine sanctuary in Mexico and has been protected since 2002. Their marine biodiversity has been documented in a series of papers in the last decade, but only three species of polychaete worms have been reported.Sixteen species of sedentary polychaete worms belonging to the families Maldanidae, Oweniidae, Sabellariidae, Sabellidae and Serpulidae are reported to the Bahía de Chamela Islands Sanctuary, 15 of these species constituting the first records in the area.Isocirrus tropicus(Monro, 1928) (Monro 1928) andNotaulax californica(Treadwell, 1906) (Treadwell 1906) constitute new records to Mexico;Idanthyrsus mexicanusKirtley, 1904 (Kirtley 1994) is first recorded since its description and one species of bamboo worm (Maldanidae) is described as new to science. The new species belongs to the genusClymenuraVerril, 1900 (Verrill 1900) and its characterised by the presence of a glandular shield on chaetiger 8; a cephalic plaque oval with smooth margins and a rounded palpode; nuchal organs straight, parallel, almost full length of plaque; manubriavicular uncini present from chaetiger 1 with 3–4 teeth above the main fang without hairs or bristles; two pre-anal achaetous segments with tori; an anal funnel with alternating triangular cirri, being the longest that are located mid-ventrally.