Uromyrtus allisoniana and Rhodomyrtus takeuchii (Myrtaceae: Myrteae) are described as new species from ultrabasic substrates in the Kamiali Wildlife Management Area, Papua New Guinea. Both species are known only from the type gatherings, and each is tentatively assigned the status of “vulnerable” following IUCN criteria. Uromyrtus allisoniana resembles U. novoguineensis from New Guinea, but differs by its indumentum type, leaf size and apex, and its flush adaxial secondary leaf veins. Rhodomyrtus takeuchii resembles R. psidioides from Australia, but differs by its solitary flowers. An updated key is provided for the genus Rhodomyrtus.