Ulcerative colitis is a chronic inflammatory bowel disease of unknown etiology, associated with extraintestinal manifestations, including the rarely reported immune thrombocytopenic purpura. Here, we present a case of immune thrombocytopenic purpura associated with preexisting ulcerative colitis. The patient was diagnosed with ulcerative colitis 13 years ago. Two years after diagnosis, he presented with hematochezia and active ulcerative colitis. Despite steroid use, the platelet count gradually decreased to 21,000/mm³. Hematochezia and the platelet count recovered after the administration of cyclosporine, and ulcerative colitis was in near complete remission for 11 years. However, the patient was re-admitted for hematochezia and thrombocytopenia persisting over a month. Medical management including increased doses of steroids in combination with cyclosporin failed to control hematochezia and thrombocytopenia. Immune thrombocytopenic purpura was suspected on the basis of normocellular marrow with a normal number of megakaryocytes. To treat uncontrolled colitis and steroid-refractory thrombocytopenia, total proctocolectomy with ileal pouch-anal anastomosis and splenectomy were performed. The patient was followed up for 10 months after surgery and was found to be in good health with a normal platelet count. Therefore, colectomy alone or in combination with splenectomy should be considered in cases of life-threatening ulcerative colitis complicated with steroid-refractory immune thrombocytopenic purpura.