This article reports a case of posterior left retroperitoneal Ewing sarcoma complicated by renal vein and inferior vena cava tumor thrombus.The patient was admitted due to "left-sided abdominal pain for one month". PET-CT scan revealed a large mass in the left adrenal region, the left adrenal gland was indistinct, and the tumor boundaries with the gastric fundus, pancreatic tail, and upper pole of the left kidney were unclear; tumor thrombus formation was suspected in the left renal vein and inferior vena cava, pulmonary artery tumor thrombus was suspected in the main trunk of the right pulmonary artery, right middle pulmonary artery, and right lower pulmonary artery. After discussion by the multidisciplinary team at Nanfang Hospital, Southern Medical University, a combined thoracoabdominal left retroperitoneal mass resection, renal vein and inferior vena cava tumor thrombus removal, and pulmonary artery tumor thrombus removal were performed. Postoperative pathology results indicated Ewing sarcoma. After a multidisciplinary consultation of difficult cases in Guangdong Urological Association, It was ultimately determined to administer adjuvant chemotherapy first postoperatively, with a regimen of VDC/IE (vincristine + doxorubicin + cyclophosphamide alternating with ifosfamide + etoposide). Retroperitoneal masses complicated by renal vein and inferior vena cava tumor thrombus present significant surgical challenges and high risks, as tumor thrombus detachment can lead to serious complications such as pulmonary artery embolism. These patients require multidisciplinary discussion before surgery, thorough preoperative preparation, multidisciplinary collaboration during surgery, and individualized postoperative adjuvant treatment.