Localized mesothelioma is a primary pleural tumor that induces hypoglycemia rarely. We experienced a case of the localized mesothelioma that induced hypoglycemia. The patient was 70 year-old man who was admitted to Severance Hospital because of general weakness and mental confusion in morning before breakfast. He was found to have low level of fasting blood sugar and C-peptide, but had normal serum insulin level. After excision of the tumor, the patient was free from symptoms of hypoglycemia, and fasting blood sugar level was returned to normal range. The most likely speculation of causing hypoglycemia by the mesothelioma was thought to be that the tumor did not secrete insulin itself but the undetectable insulin-like substance and/or antigluconeogenic substances. During the follow up, 5 months after surgical removal of tumor, the patient was in a good condition without symptoms of hypoglycemia.