Several polychaetes species from the central Cantabrian (NE Atlantic Ocean) and western Mediterranean Seas were studied. The Fabriciidae species Parafabricia mazzellae and Pseudofabricia aberrans are recorded for the first time in the western Mediterranean Sea and Novafabricia infratorquata in the northeast Atlantic Ocean (Cantabrian Sea). A new species of Polycirridae, Polycirrus asturiensis sp. nov., is described for the Cantabrian Sea; it is characterized by having two types of buccal tentacles, a transverse prostomium covering segment 1, a trilobed upper lip, notopodial lobes equally long, notochaetigerous segments with broadly winged chaetae of different lengths and widths, up to segment 12, and type-1 neurochaetae beginning on segment 6. New habitat information for the fabricids Novafabricia infratorquata, Parafabricia mazzellae and Pseudofabricia aberrans is also provided.