Mossman virus (MoV) was isolated on two occasions from wild rats trapped in Queensland, Australia, during the early 1970s. Together with Nariva virus and J-virus MoV belongs to a group of novel paramyxoviruses isolated from rodents during the last 40 years, none of which had been characterized at the molecular level until now. cDNA subtraction strategies used to isolate virus-specific cDNA derived from both MoV-infected cells and crude MoV pellets were pivotal steps in rapid characterization of the complete genome sequence. Analysis of the full-length genome and its encoded proteins confirmed that MoV is a novel member of the subfamily Paramyxovirinae which cannot be assigned to an existing genus. MoV appears to be more closely related to another unclassified paramyxovirus Tupaia paramyxovirus (TPMV), isolated from the tree shrew Tupaia belangeri. Together with Salem virus (SalV), a further unclassified paramyxovirus that was isolated from a horse, MoV and TPMV make up a new collection of paramyxoviruses situated evolutionally between the genus Morbillivirus and the newly established genus Henipavirus.