Molecular and morphological data support the recognition of seven species of Chiastocaulon in Australia, of which four, namely C. braunianum and C. geminifolium comb. nov. from tropical north-eastern Queensland and C. proliferum and C. flamabilis sp. nov. from Tasmania (and New Zealand), represent new records. The other three species accepted for Australia are C. biserialis, C. dendroides and C. oppositum. Chiastocaulon conjugatum is excluded from the Australian flora, because previous Australian records are based on misidentifications of C. braunianum and Plagiochila retrospectans. Pedinophyllum monoicum, reported for Australia from a single locality in Victoria, is excluded from the Australian flora because all credible records are based on misidentifications of Syzygiella tasmanica. The Papua New Guinean Chiastocaulon takakii comb. nov. is reinstated from synonymy under C. dendroides on the basis of morphological evidence. Descriptions and illustrations of all Australian species, and dichotomous keys to species of the Chiastocaulon lineage in Australia and New Zealand, are provided.