A case of benign mesothelioma of the tunica vaginalis testis is described. A 56-year-old man with no history of asbestos exposure presented with a swelling of the left scrotal content. A physical examination revealed a hydrocele and an induration on the left epididymal head. A cytological examination of the hydrocele fluid demonstrated clusters of mesothelial cells without evidence of malignancy (class III). Left inguinal orchiectomy was performed because a 15 mm papillary pedunculated tumor was seen on the surface of the tunica vaginalis. A microscopic examination showed the papillary and glandular structures composed of cuboidal cells with no cytologic atypia, which were consistent with benign mesothelioma. The patient remains well and free of recurrent disease 10 years after operation.