Fifty-five Plagiochila species are recognized for Australia and New Zealand. Nine of these are new, all from Australia eight of which come from the Wet Tropics Bioregion of north east Queensland and one from the south-eastern mesic archipelago. Four of the new species belong in the challenging, and neglected, section Vagae. Three species are new Australian records, P. daviesiana, P. monospiris, and P. streimannii; and one species, P. alta, is a new record for New Zealand. Six species, P. annotina, P. circumdentata, P. colensoi, P. deltoidea, P. gigantea and P. ramosissima, are excluded from Australia as these are all New Zealand endemics reported in error for Australia. One New Zealand species is reported new for Australia (P. baylisii). Four species are excluded from Australia, P. furcata, P. inflata, P. renitens and P. sciophila, as they are based on misidentifications or are not supported by voucher material or both. Another interpretation of the confusion surrounding the name Plagiochila baileyana is presented, wherein Plagiochila baileyana is accepted as a species distinct from P. gigantea, while Plagiochila aculeata is returned to synonymy of P. fasciculata, and Plagiochila subfasciculata Colenso is reinstated. The number of Plagiochila species in Australia increases from 32 to 41, but the number of species in New Zealand decreases from 28 to 27 as a result of this study. New combinations at species level are also proposed for a variety of P. blepharophora from Fiji and two varieties of P. gymnoclada from Sumatra and Java, two species which morphological data suggests are grossly polyphyletic as currently circumscribed.