Well-differentiated papillary mesothelioma (WDPM) affecting the tunica vaginalis testis is a rare tumor, and very little is known about the clinicopathological spectrum of this variant as a distinct entity. Most patients with WDPM suffer from scrotal pain or swelling, but hydrocele seems to be the most common presenting symptom. These lesions are usually not aggressive and are accompanied by an indolent clinical behavior. In this article, we report the first case known of WDPM in an undescended testis, and in addition, we review the literature for similar cases.