In 2009, an outbreak of white nodular cutaneous lesions was detected in one of only two known breeding colonies of the critically endangered southern bentwing bat (Miniopterus schreibersii bassanii), at Naracoorte, South Australia. Necropsies were conducted on 10 euthanized bats in September 2009. In October 2009, 123 bats were examined under anesthesia, with skin biopsies collected from 18 affected bats. Prevalence of skin lesions was 45.2%. The prevalence among males was three times greater than among females. The majority of lesions examined histologically were granulomas, typically centered on a nematode. A single lesion had epidermal hyperplasia with intracytoplasmic inclusions consistent with a pox virus; pox virions were identified on electron microscopy. Nematodes dissected from frozen lesions were identified morphologically as Riouxgolvania beveridgei, previously described in the eastern bentwing bat (Miniopterus schreibersii oceanensis). The factors contributing to this apparent disease emergence and outbreak remain undetermined. Lesions consistent with white nose syndrome were not identified.