We report a case of a 70-year-old male with delayed perforation in the cecum treated by endoscopic ultrasonography-guided drainage for a pelvic abscess. The lesion was a 50-mm laterally spreading tumor, and endoscopic submucosal dissection (ESD) was performed. No perforation was detected during the operation, and en bloc resection was achieved. He had fever and abdominal pain on postoperative day (POD) 2. Computed tomography (CT) revealed the intra-abdominal free air, leading to a diagnosis of delayed perforation after ESD. Vital signs were stable, the perforation was considered minor, and endoscopic closure was attempted. The colonoscopy under fluoroscopy showed no perforation in the ulcer and no leakage of the contrast medium. He was managed conservatively with antibiotics and nothing per os. Symptoms improved; however, a follow-up CT on POD 13 revealed a 65-mm pelvic abscess, and endoscopic ultrasound (EUS)-guided drainage was successfully performed. The follow-up CT on POD 23 showed the reduction of abscess, and the drainage tubes were removed. Emergent surgical treatment is crucial in delayed perforation because it has a poor prognosis, and reports of conservative therapy for colonic ESD with delayed perforation are few. The present case was managed with antibiotics and EUS-guided drainage. Thus, EUS-guided drainage can be a treatment option for delayed perforation after colorectal ESD, if the abscess is localized.