Rectal perforation is an unusual complication of therapeutic colonoscopy. The present study reports the case of a patient with a rare manifestation of pneumothorax, pneumomediastinum, pneumoperitoneum and extensive subcutaneous emphysema that resulted from an endoscopic mucosal resection following a colonoscopy of the rectum. Only 3 cases of colonic perforation and 1 case of rectal perforation have been described previously, of which the clinical diagnoses and treatments were varied, and no results of follow-up studies were reported. In the present study, dyspnea and neck swelling were acute signs of extraluminal air that resulted from rectal perforation. Computed axial tomography was an effective diagnosis method, and is recommended for the early recognition of colorectal perforation. Appropriate management and a close follow-up are crucial for optimal results.