A new species of Paramphinome (Polychaeta: Amphinomidae) is described from southern Brazil (900–2000 m). Paramphinome posterobranchiata sp. nov. differs from already described species by having a small body (1–9 mm); a low number of chaetigers (10–29); branchiae in few chaetigers (0–3) and starting more posterior than in most species; and by a reduced caruncle.