This study documents the helminth assemblages of Uromys caudimaculatus (Krefft, 1867) from Papua New Guinea and Australia as well as listing helminths found in U. anak Thomas, 1907 from Papua Indonesia and Papua New Guinea, and U. hadrourus (Winter, 1984) from Queensland Australia. In total, 36 species of helminth, comprising one acanthocephalan, three cestodes (excluding unidentifiable fragments) and 32 nematodes (including two not identified to genus) from 65 hosts were found. The Trichostrongylina nematodes were the dominant group of helminths, the most prevalent species being Odilia uromyos (Mawson, 1961), found in each of the species of Uromys across all regions, and O. melomyos (Mawson, 1961), occurring in U. caudimaculatus from Papua New Guinea and Australia. The helminth species assemblage from U. caudimaculatus, 14 species of helminth from 11 hosts from Papua New Guinea and 23 species of helminth from 51 hosts from Australia, had high species richness but was relatively equitable overall (1/SI = 0.92). The differences found between the helminth assemblages of U. caudimaculatus from Papua New Guinea and Australia suggest that U. caudimaculatus may have travelled to Australia from New Guinea with a small pool of helminth species that was subsequently added to by host switching from sympatric rodent hosts. Alternatively, U. caudimaculatus may have lost many of the helminths that travelled with it following arrival in Australia.