Alentiana has only one member, A. aurantiaca (Verrill, 1885), commensal with sea anemone (Bolocera tuediae). Here, Alentiana palinpoda sp. nov., a second member in the genus Alentiana (subfamily Lepidastheniinae), a new commensal polynoid is described, based on a specimen collected from a deep-water seamount in the Northwest Pacific Ocean. The new species is characterized by large elytra that completely cover the dorsum and are present in every third segment in the posterior regions. Neuropodia are truncated, with two types of neurochaetae; supraacicular chaetae toothed on one side with a slightly inflated end, and subacicular chaetae that are heavy and smooth; the prechaetal lobe is larger than the postchaetal lobe, with the ventral part rolling upward and backward.