A 32-year-old woman was admitted with intermittent rectal bleeding with disseminated intravascular coagulation (DIC)-like coagulopathy. CT and MRI revealed a retroperitoneal tumor, and we diagnosed giant retroperitoneal hemangioma complicated with Kasabach-Merritt syndrome, following blood pool scintigraphy. Corticosteroid and interferon-alpha were not effective, and gabexate mesilate was also ineffective for coagulopathy. Immediately after receiving danaparoid sodium, she recovered from DIC. We performed tumor resection successfully, and she had no symptoms of coagulopathy thereafter.