Background: Ovarian carcinoma usually presents in an indolent manner. A patient with ovarian cancer rarely shows acute clinical features which require immediate medical intervention. Case: We present a 36-year-old Japanese woman with an ovarian tumor, who suffered general fatigue and increased abdominal girth on admission. Her hemoglobin, platelet count and fibrinogen were decreased, and fibrin/fibrinogen degradation products were elevated, which determined the diagnosis of disseminated intravascular coagulation (DIC). Since computed tomography scan and magnetic resonance imaging revealed an intratumoral hemorrhage, an emergency laparotomy was performed. The patient was found to have ovarian cancer with a massive intratumoral hemorrhage, and DIC improved immediately after the operation. Conclusion: The clinician should be alert to the possibility that intratumoral bleeding of ovarian cancer might be associated with DIC.