Malacoceros samurai, new species, (Spionidae) is described from deep-sea hydrothermal vents of the southern East Pacific Rise, at 17°25′S. It is a large species, living on chimney walls along with Avinella spp. Although this species is described in the genus Malacoceros, it possesses unidentate hooded hooks and anterior scalpel-like aristate neurosetae, both characters which clearly differentiate it from other species of the same genus. These unusual characters require the modification of the generic diagnosis of Malacoceros.