Infantile hemangioendothelioma (IHE) is a rare benign vascular tumor with potentially life-threatening complications. Various therapeutic options have been recommended according to the site, extent, and behavior of the IHE. Because of the slow and unpredictable response to treatment with using a single drug in critically ill patients, there is a tendency to administer drugs in combination to treat this disease. Here, we report on a 1-month-old female infant who had a retroperitoneal IHE with Kasabach-Merritt syndrome and she was successfully treated with a combination of steroid, interferon-alpha, and vincristine.