Background: Primary ovarian angiosarcoma arising from a mature cystic teratoma is a very rare tumor, known to be very aggressive and respond poorly to chemotherapy. However, little information exists regarding the treatment of this disease. Case: Here, we report the first case of a teenage girl diagnosed with primary ovarian angiosarcoma arising from a mature cystic teratoma. The patient received no adjuvant treatment after primary surgery. Despite stage I disease, the patient presented with metastatic tumors within two months postoperatively. She died of a fatal hemorrhage presumed to occur in metastatic tumors after receiving delayed chemotherapy. Conclusion: Because primary ovarian angiosarcoma arising from a mature cystic teratoma can be found in young women, early diagnosis and proper treatment are essential. The tumors grow rapidly and are fragile enough to rupture, so it is reasonable to prescribe early adjuvant treatments after optimal debulking surgery before progression or recurrence. Treatment of the recurrent or metastatic tumors should be performed with caution because complications, such as severe bleeding, may arise from the hemorrhagic tumors.