We herein report a rare case of a 47-year-old man with a primary mature retroperitoneal malignant teratoma. The patient received neoadjuvant chemotherapy and the residual tumor was resected. A histopathological examination confirmed the diagnosis of malignant teratoma with endodermal, ectodermal, and mesenchymal structures. The patient is alive and disease free at 13 months after resection.