The authors report a case of intra-abdominal synovial-sarcoma of the gastrocolic ligament in a 64-years-old woman hospitalized for a palpable abdominal mass and pain. CT scan detected an intra-abdominal mass extended through the abdominal wall into the soft tissues, causing compression and dislocation of intra-abdominal structures (left liver, gallbladder, pylorus and gastric antrum, duodenal bulb). At its back, it was in contact with the pancreas, the vena cava and the right kidney. Biopsy revealed that the mass was an intra-abdominal synovial-sarcoma. Patient received preoperative chemotherapy. After three chemotherapy cycles the patient was admitted to hospital for anemia. CT-scan revealed mass necrosis and bleeding. After red blood cells transfusions, the patient underwent surgery and the mass was resected. Histopathological study confirmed the diagnosis of biphasic Synovial-Sarcoma. SYT-SSX1/2 fusion molecular assessment was attempted, but it was not possible to evaluate the presence of the t (X, 18) (p11.2; q11.2) traslocation. The patient was discharged in good health and received adjuvant chemotherapy. CT-scan after 18 months showed pulmonary and intra-abdominal relapse of the disease.