A 29-year-old man with a right lower abdominal tumor was found in preoperative abdominal computed tomography (CT) to have a 10cm retroperitoneal tumor with cystic components excluding the external iliac artery. Abdominal angiography showed that the tumor fed on a branch of external iliac artery. Only AFP was elevated. We diagnosed this case as yolk sac tumor, conducting retroperitoneal tumor resection. Microscopically, spindle-shaped tumor cells were tightly arranged. Immunohistochemistry showed the tumor to be positive for AFP, placental alkaline phosphatase (PLAP), and human chorionic gonadotropin (hCG). The final pathological diagnosis was retroperitoneal yolk sac tumor. After surgery, a right testicular tumor became obvious, which we resected. We also conducted combined PBSCT and salvage high dose chemotherapy against the remnant tumor. The patient had no evidence of recurrence or metastasis in the 13 months after chemotherapy. Tumor markers may thus be effective in qualitatively diagnosing of retroperitoneal tumor, and multidisciplinary therapy is important.