Primary nasal-type natural killer/T-cell lymphoma of the testis is a rare malignancy. Although dissemination to the testis from other sites occurs somewhat more frequently than a primary presentation, even secondary testicular involvement is uncommon. In this article, the authors report on the comprehensive histopathologic, immunohistochemical, and molecular analysis of a case of primary testicular nasal-type natural killer/T-cell lymphoma, and review the features of 16 previously reported patients. The investigation carried out in this study indicates that the testicular nasal-type natural killer/T-cell lymphomas occur at a younger age than their B-cell counterparts, express cytoplasmic CD3 and surface CD56, and consistently show an infection by Epstein-Barr virus. These tumors have variable expression of T-cell antigens other than cytoplasmic CD3 and may show monoclonal rearrangement of T-cell receptor genes. Testicular natural killer/T-cell lymphomas of nasal type invariably follow an aggressive clinical course.