Background: Mesothelioma of the tunica vaginalis testis is a rare and aggressive cancer; fewer than 90 cases have been reported. It occurs in all age groups, but its highest incidence appears between 55 and 75 years of age. Less than 5% of all malignant mesotheliomas arise from the tunica vaginalis testis. Case Report: The authors present a rare case of localized malignant mesothelioma of the tunica vaginalis testis. Diagnosis and treatment are described. Conclusion: Mesothelioma of the tunica vaginalis testis can be asymptomatic for a long time. In more than half of the cases, the clinical manifestations imitate a hydrocele or a tumor mass in the scrotum. Despite treatment, this tumor has a very poor prognosis with a median survival of 23 months.