We report a case of acute disseminated intravascular coagulation (DIC) developed during menstruation in an adenomyosis patient. No known predisposing factor for DIC such as infection or pregnancy was involved in this case. As anticoagulation therapy and supplementation of coagulation factors quickly improve the state, surgical removal of the uterus was not required. We speculate that hemorrhage in the adenomyosis legion and subsequent local thrombosis played crucial role in pathophysiology of this case of acute DIC.