Angiosarcoma is a rare malignant tumor with an aggressive clinical course and a poor prognosis. Intraperitoneal angiosarcoma, especially originating from the omentum, is extremely rare. We report a case of radiation-induced angiosarcoma of the omentum that arose in a 38-year-old female seven years after concurrent chemoradiotherapy for cervical cancer. The primary tumor was unknown until diagnostic laparoscopy revealed an unresectable omental mass. Pathological examination revealed high-grade malignant cells positive for endothelial markers. Although the small number of cases limits the consensus on optimal therapy for advanced angiosarcoma, the patient was managed successfully by taxane-based chemotherapy, leading to complete response and consequent complete cytoreductive surgery. Our report is the fifth case of radiation-induced angiosarcoma of the omentum, and all have developed after treatment for gynecologic cancer. Although very rare, this complication should be considered after radiation therapy in cancer treatment, particularly given the increasing importance of this therapy.