We present the case of a 62-year-old man with a malignant Brenner tumor of the testis and epididymis. The neoplasm showed the distinctive histologic features of Brenner tumors of the ovary, including the presence of nests of transitional epithelium with focal mucinous differentiation, surrounded by septae of dense fibrous tissue. In addition to areas of typical Brenner epithelium, the tumor displayed a component of transitional and squamous carcinoma that invaded the testicular parenchyma, epididymis, and vas deferens, and metastasized to periaortic lymph nodes. To our knowledge, there are only four previously described instances of testicular Brenner tumors. Our case appears to represent the first description of a malignant Brenner tumor of the testis and epididymis.