We report a first case of paraneoplastic human chorionic gonadotropin (HCG) production in a dedifferentiated liposarcoma with rhabdosarcomatous differentiation in an 83-year-old man with a retroperitoneal mass, unilateral scrotal enlargement, and a serum HCG level of 843 IU/L. Core biopsy of the retroperitoneal mass revealed rhabdomyosarcoma. Orchiectomy revealed a paratesticular dedifferentiated liposarcoma with rhabdosarcomatous differentiation. Fluorescence in situ hybridization analysis performed on both the retroperitoneal and paratesticular masses revealed amplification of MDM2. The retroperitoneal tumor was interpreted as metastatic dedifferentiated liposarcoma with the dedifferentiated component represented by rhabdomyosarcoma. HCG production is a common feature of testicular germ cell tumors, less common in carcinomas, and extremely rare in sarcomas. Accordingly, sarcomas secreting HCG are a potential diagnostic pitfall, and raise the differential diagnosis of germ cell tumors and a variety of carcinomas. HCG production by carcinomas is a known poor prognostic finding, however the significance of its production in sarcomas is unknown.