Species in the parasitic isopod family Cabiropidae are known to utilise various isopods as hosts but there are currently no records of members parasitising anthuroid hosts. We describe Anthuroniscusgen. nov. for three new cabiropid species, Anthuroniscus shimomuraisp. nov., Anthuroniscus dentatussp. nov. and Anthuroniscus latussp. nov., all of which are parasitic on anthuroid isopods. Anthuroniscusgen. nov. differs from the other 14 cabiropid genera and 10 genera treated as family incertae sedis in females having an elongate, dorsally compressed, posteriorly tapering body with six pairs of lateral bulges; and cryptoniscus larvae in the following combination of characters: (1) eyes lacking, (2) antennular article 1 with eight teeth on the posterior margin, (3) uropodal exopod and endopod rectangular rather than tapering, and endopod longer than exopod, and (4) pleotelson trapezoidal, 2× as wide as long. Anthuroniscus shimomuraisp. nov. was parasitic on Mesanthura sp. from Kaichu Doro, Uruma, Okinawa, south-western Japan; A. dentatussp. nov. on Accalathura sp. from Irabu Island, Miyako Islands, Okinawa; and A. latussp. nov. on Colanthura nigra from Kanagawa, central Japan. In pairwise comparisons, the three new species showed p-distances of 0.6–1.3% for the 18S rRNA gene (1440 positions); and A. shimomuraisp. nov. and A. latussp. nov. showed a p-distance of 36.2% for the 16S rRNA gene (412 positions). In an 18S-based maximum-likelihood tree, an Anthuroniscusgen. nov. clade was the sister group to Cryptoniscoidea sp., parasitic on an ostracod species. This is the first study reporting Cabiropidae from Japan and anthuroids as hosts for Cryptoniscoidea. ZooBank: urn:lsid:zoobank.org:pub:2EE042E2-AE48-4B87-B495-8436462146B9