Proteus syndrome is a rare hamartomous disorder with highly variable manifestations of disproportionate overgrowth of body parts, epidermal nevi and vascular malformations. We describe two patients who had typical clinical and imaging Proteus syndrome features. One of most characteristic findings in these two patients was that they had giant hemangiomas of the spleen that caused Kasabach-Merritt syndrome, demonstrating clinical bleeding and disseminated intravascular coagulation laboratory alterations. The present two cases are the first report of this complication in Proteus syndrome. The patients' bleeding tendency and hemostatic defects were completely corrected after they successfully underwent splenectomy.