Since elderly patients with systemic diseases often undergo tooth extraction, it is difficult to predict the risk of and to optimally treat post-extraction hemorrhage. We report a rare case of persistent hemorrhage that occurred after tooth extraction caused by chronic disseminated intravascular coagulation (DIC) as a complication of dissecting aneurysm. A 69-year-old man who underwent extraction of a maxillary molar had persistent bleeding, which could not be stopped by continuous local treatment to promote hemostasis. After a general examination, we diagnosed chronic DIC caused by an extensive dissecting aneurysm, based on evidence of advanced fibrinogenolysis. Hemostasis was achieved by general treatment for chronic DIC. Appropriate diagnosis and treatment of both local and general conditions are necessary for post-extraction hemorrhage.