A 3-year-old male nanday conure (Nandayus nenday) was presented with acute lethargy, polyuria, and polydipsia. Marked persistent hyperglycemia, glycosuria, and ketonuria were also noted. The serum insulin concentration (<3 μU/ml) was lower than reference ranges described for other psittacine birds. Initial treatment included insulin, antibiotics, and supportive care. Insulin therapy was adjusted based on results of serial blood glucose curves. Histopathologic examination of pancreatic biopsy samples revealed normal exocrine pancreatic tissue with rare lymphoplasmocytic infiltrates and absence of pancreatic islets, suggesting atrophy of endocrine pancreatic tissue. Resolution of clinical signs and a normalized blood glucose curve were obtained after administration of long-acting insulin (0.3 IU/kg IM am and 0.25 IU/kg IM pm). One month after initial presentation, the conure was admitted for severe dyspnea and lethargy and died despite supportive care. Histopathologic examination of the pancreas revealed nearly total depletion of the endocrine pancreas with moderate lymphoplasmocytic pancreatitis. Immunohistochemical evaluation of the remaining pancreatic islets was negative for the presence of insulin and positive for glucagon. Results of polymerase chain reaction tests for Chlamydophila psittaci performed on tissues from the liver, spleen, and lung were negative. Transmission electron microscopy did not demonstrate viruses. Clinical and pathological findings observed in this case are consistent with insulin-dependant type 1 diabetes.