We report a patient with Type 2 diabetes mellitus complicated by neuropathy affecting the phrenic nerves, resulting in fatal respiratory failure. Diabetic mononeuropathy is common and usually recovers spontaneously, but bilateral phrenic nerve involvement appears to be uncommon and difficult to treat. The pathology of diabetic mononeuropathy is not well understood and we believe this to be the first histological report of a phrenic nerve biopsy in this condition.