Transthoracic ultrasound has been widely accepted for the evaluation of many thoracic diseases, including pleural effusion, atelectasis, pneumothorax, and pneumonia with subpleural effusion. Application of ultrasonography for the diagnosis of pneumothorax is an effective and timely intraoperative technique. We herein present a patient who developed pneumothorax following diaphragmatic injury during laparoscopic cholecystectomy. The pneumothorax was rapidly identified by bedside ultrasound. The compressed lung was successfully re-expanded using positive end-expiratory pressure (PEEP) ventilation under real-time ultrasound monitoring, and closed thoracic drainage was avoided. Therefore, the correct use of ultrasound can identify the adequate PEEP level that is able to promote resolution of pneumothorax induced by diaphragmatic injury.