Malignant mesothelioma of the tunica vaginalis testis is a rare aggressive neoplasm with fewer than 100 cases reported in the world literature. Because of its nonspecific symptoms, wide age distribution, and absence of tumor markers, most cases have been diagnosed intraoperatively. A small number of case reports have illustrated the typical sonographic appearance of this tumor, but in only 1 case has imaging led to a preoperative diagnosis. Color Doppler images have been documented with the advancement of imaging technology, but all of these cases lacked appearances specific for malignancy. We describe a case of malignant mesothelioma of the tunica vaginalis with typical sonographic and previously unreported color Doppler characteristics.