Chronic disseminated intravascular coagulation (DIC) complicates 5.7% of thoracic aortic aneurysm. DIC with thoracic aortic aneurysm is characterized by hyperfibrinolysis, but usually shows a stable condition in a state of compensated non-overt DIC with limited hemorrhagic symptoms. However, in some cases, hemorrhage caused by external factors may induce uncompensated overt DIC and lead to serious hemorrhagic tendencies. In the present study, we report a patient with a thoracic aortic aneurysm complicated by DIC who exhibited marked hemorrhagic tendencies. DIC remarkably improved following administration of recombinant human soluble thrombomodulin.