A 2-year-old sun conure (Aratinga solstitialis) was examined because of acute lethargy and depression. Physical examination revealed severe weakness with ventroflexion of the head and neck and seizure episodes precipitated by handling. Empirical and supportive care was instituted, and serial diagnostic testing revealed no specific diagnosis or etiology. Antemortem test results for West Nile virus were negative. After 2 weeks of a deteriorating clinical condition, euthanasia was elected and necropsy was performed. Gross examination revealed no significant lesions; however, histologic examination of brain tissue revealed perivascular cuffing of mononuclear inflammatory cells in the cerebrum and mild perivascular, lymphocytic, and plasmacytic infiltrates scattered in the grey matter of the cervical spinal cord. Viral isolation of brain tissue was positive for West Nile virus.