A Dieulafoy lesion of the rectum is a very rare entity that can cause massive lower gastrointestinal (GI) hemorrhage. Identifying the bleeding point is sometimes difficult because these lesions are very small. We herein describe an 82-year-old man with active hemorrhage due to a rectal Dieulafoy lesion. He was referred to our hospital because of persistent hematochezia from the morning of that day. He had a history of atrial fibrillation, chronic heart failure, diabetes mellitus, and hyperuricemia. Prompt multidetector-row computed tomography (MDCT) enabled us to detect active bleeding from the lower rectum. Subsequently, colonoscopy revealed an exposed vessel in the lower rectum without surrounding ulceration, and hemostasis was successfully achieved using a hemostatic forceps with soft coagulation. After hemostasis had been achieved, the patient recovered and was discharged without complications and rebleeding. He is doing well 6 months after discharge from the hospital. Sequential examination by MDCT and colonoscopy is considered an efficient treatment strategy for patients with active lower GI bleeding.