A 48-year-old woman who was without any abnormal past medical history underwent colonoscopy as a screening procedure for colorectal disease. The procedure was uneventful and there was no sign of inflammation around the appendicular orifice or the luminal surface of the cecum. The patient did not complain of pain or significant discomfort throughout the procedure. She then developed pain in the right lower quadrant of the abdomen that evening and this persisted for four days. She visited the outpatient department and underwent abdominal ultrasonography, which showed a swollen appendix with a collection of pericecal fluid. Surgical exploration and appendectomy were performed; the final diagnosis was acute suppurative appendicitis. Colonoscopists should be aware of this rare complication and consider it when making the differential diagnosis of post-colonoscopy abdominal pain.