Abstract Nine morphologically distinct species of Macvicaria Gibson & Bray, 1982 were recovered from six families, ten genera and twelve species of marine fishes in the waters off the coast of Queensland, Western Australia and South Australia: M. shotteri n. sp. in Apogon fasciatus (type-host), Sillaginodes punctatus and Sillago bassensis from Moreton Bay (type-locality), off southern Western Australia and off Kangaroo Island, South Australia; M. mekistomorphe n. sp. in Sillago maculata from Moreton Bay; M. mutovitellina n. sp. in Dactylophora nigricans from off southern Western Australia; M. flexuomeatus n. sp. in Goniistius gibbosus (type-host) and Cheilodactylus rubrolabiatus from southern Western Australia; M. vitellocopiosa n. sp. in Sillaginodes punctatus from off Kangaroo Island, South Australia; M. dextrocaula n. sp. in Notolabrus parilus (type-host) and N. fucicola (Richardson) (Labridae) from off southern Western Australia (type-locality) and Kangaroo Island, South Australia; M. heronensis Bray & Cribb, 1989 in Trachinotus coppingeri off Stradbroke Island, Queensland; M. adomeae n. sp. in Sillaginodes punctatus off Kangaroo Island, South Australia; M. kingscotensis n. sp. in Neoodax balteatus (type-host) and Haletta semifasciata off Kangaroo Island, South Australia. We have used the following characters to distinguish between the species of Macvicaria: general body form; length/width ratio; size of cirrussac; length of forebody; post-testicular extent of caeca; egg size; and the position of the genital pore. Most of the species of Macvicaria showed interspecific differences in all of the characters enumerated, the most dramatic being in the position of the genital pore in one species. All 11 specimens recovered from 2 species of Notolabrus were found to have a dextral genital pore. This is the second report of amphitypy in the Opecoelidae. All of the host species, apart from Apogon fasciatus, are endemic to Australian or Australian and New Zealand waters. New combinations formed are: M. dactylopagri (Manter, 1954); M. deeghaensis (Gupta & Gupta, 1988); M. eleuthoronemae (Wang, Wang & Zhang, 1992); M. gerridis (Fischthal & Thomas 1970); M. hunghuaensis (Qiu & Li in Shen & Qiu, 1995); M. longicirrata (Manter, 1963); M. oligolecithosus (Wang, Wang & Zhang, 1992); M. synagris (Yamaguti, 1952).