Mazatlan is the main sea and coastal port from northwestern Mexico. There are maritime metallic signaling buoys throughout the navigation channel, these provide a favorable substrate for the establishment of diverse fouling communities. This study discloses the composition of errant eunicemorph and phyllodocemorph polychaete species associated to metallic buoys during an annual cycle (2009). The polychaetofauna is represented by 6 families, 17 genera and 22 species. Nine are nominal species, seven are potentially new species and six require of detailed studies to clarify their identity. Pterocirrus (Phyllodocidae) is recorded by the first time in the Tropical Eastern Pacific. The habitat, distribution and taxonomic comments of the recorded species are indicated; furthermore, a fouling polychaete species list in the Gulf of California is included.