Three new species belonging to new monotypic genera from Western Australia are added to the phreatoicidean isopod family Amphisopodidae: Eremisopus beei n.gen., n.sp. from the northwestern Kimberley region, Peludo paraliotus n.gen., n.sp. from Cape le Grand on the southern coast, and Platypyga subpetrae n.gen., n.sp. from Stirling Range. All species are illustrated using scanning electron micrographs. Both Ciliophora and ostracode Crustacea were found as epibionts on these species. All three isopod genera have highly restricted geographic distributions and could be threatened by anthropogenic degradation of their environments. Western Australia now has eight described genera of Amphisopodidae and Hypsimetopodidae, a generic diversity similar to Tasmania. Members of the Phreatoicidae, however, are absent in Western Australia. The distribution of Western Australian phreatoicideans suggests that they may have originally diversified in East Gondwana, while the Phreatoicidae show relationships to West Gondwana. A key to genera of Western Australia Phreatoicidea is included.