The purpose of this paper was to describe an unusual manifestation of a sarcoma of the spleen and to raise awareness for spontaneous rupture of the splenic vessels in patients with splenic tumors. A 70-year-old man was admitted to our institution, suffering from left upper quadrant abdominal pain. Upon physical examination, a large and tender abdominal mass was palpated. Abdominal computed tomography showed a heterogenous enlarged spleen with active contrast extravasation from the splenic artery, free intraperitoneal fluid, and a retroperitoneal hematoma. The patient was treated with angioembolization of the splenic artery. Because of rebleeding, splenectomy was performed. Pathology revealed the spleen to be involved with an unclassified malignant spindle cell neoplasm. We concluded that in the case of spontaneous rupture of the splenic artery, accompanied with a radiologic appearance of an enlarged spleen, the diagnosis of sarcoma should be included in the differential diagnosis.