Unixenus Jones, 1944 (Polyxenidae) is the dominant genus of penicillate millipedes found throughout mainland Australia. Herein, a new species, Unixenus mossmanussp. nov., is described from coastal forest near Mossman. The new species is similar to U. karajinensis, sharing the same sensilla pattern on antennal article VI and the same arrangement of leg setae. Unixenus mossmanus sp. nov. differs by having only 3 ornamental trichomes c per side (v. 5-9), 2 pairs coxal glands in the male (v. 6 pairs), and a slender claw (v. robust). These characteristics differ from those of U. karajinensis, which has 5–9 ornamental trichomesc; 6 pairs coxal glands in male; and a robust claw structure. 18S sequence of Unixenus mossmanus sp. nov. is included. Diplopoda, Polyxenidae, Unixenus, Queensland, Australia.