Malignant epithelioid mesothelioma of the tunica vaginalis of the testis is very rare. It is often diagnosed accidentally by histologic examination of the hydrocelectomy wall preparation. The aggressiveness and poor prognosis of this tumor require radical surgery as the primary therapy. We describe the case of a 45 year old patient, in whom an epithelioid mesothelioma was incidentally detected after hydrocelectomy.