This is a report on the anesthetic management of a patient who undertook screening colonoscopy under intravenous sedation and experienced a perforation over an invasive colonic tumor located at splenic flexure, resulting in pneumoperitoneum, pneumothorax, pneumomediastinum, and pneumopericardium. The patient recovered well after resection of the lesion through laparotomy. In this report, colonoscopy-related complications and pathophysiology as well as the anesthetic plan are discussed.