A crossbreed dog with a history of a chronic progressive tetraparesis had an insulinoma-related peripheral polyneuropathy. Frequent feeding and treatment with corticosteroids resulted in recovery from a non-ambulatory to an almost completely normal clinical state, despite the persistence of hypoglycaemia and hyperinsulinism. After euthanasia for uncontrollable seizures, the presence of a beta-cell carcinoma of the pancreas and extensive axonal degeneration of the peripheral nerves was confirmed by histopathological examination. These findings may indicate an immune-mediated pathogenesis for insulinoma-related peripheral polyneuropathy.