This paper describes the pathology associated with psittacine beak and feather disease in a wild sulphur-crested cockatoo with concurrent knemidocoptic mange, cestodiasis and mycotic encephalitis. Methods & Results Large numbers of Knemidocoptes pilae Lavoipierre and Grifﬁths, 1951 (Acari: Epidermoptidae, Knemido-koptinae) were identiﬁed in affected skin associated with enhanced expression of beak and feather disease virus (BFDV) determined by immunohistochemistry. Also, BFDV antigen was demonstrated in high concentration in the gut and faecal sacs of mites, raising the possibility of ectoparasites as fomites and vectors of BFDV transmission. Large numbers of Raillietina spp. cestodes were present in the intestines. Within the brain there was a focally extensive region of necrosis and inﬂammation associated with branching, septate, pigmented hyphae consistent with zygomycete fungal infection. Conclusion This case highlights the potential immunosuppressive effects of BFDV infection and its potential as a keystone pathogen in the Australian environment.