Elisesione imajimai sp. nov. is newly described based on specimens collected in Sagami Bay, Japan, at a depth of 150-250 m. This new species resembles E. problematica (Wesenberg-Lund, 1950) from Iceland, but differs because in E. imajimai sp. nov. the ventral cirri surpass the tips of the neurochaetal lobes, reaching to the medial part of the neurochaetal bundle; the palps are 1/2 – 4/5 as long as the antennae; the aciculae are pale brownish; and the dorsal integument shows 9-10 transverse wrinkles per segment, whereas in E. problematica the ventral cirri hardly reach the tips of the neurochaetal lobes; the palps are as long as the antennae; the aciculae are black; and there are 15 transverse wrinkles per segment. A morphological redescription of E. problematica based on its type material and a revised key to identify species in the genus are also provided. A phylogenetic analysis based upon four genes (COI, 16S, 18S, 28S) confirms its position within Hesionini.