Phosphatic concretions containing mineralized three-dimensional plant and invertebrate tissues occur in a mid-Cenozoic terrestrial freshwater carbonate deposit at the Riversleigh World Heritage area in northwestern Queensland, Australia. Mineralogical composition and microstructure of the concretions show that this fossil assemblage was preserved by rapid, early diagenetic phosphatization. Preserved material includes tissues typically considered to have a poor potential for phosphatization, such as internal plant structure and arthropod exoskeletal components. Phosphatization may have been mediated by the presence of microbial films. Study of this rich assemblage has the potential to make significant contributions to both the Australian Cenozoic terrestrial invertebrate fossil record and the Cenozoic plant megafossil record of northern Australia.