Pneumomediastinum, air within the planes of the mediastinum, occurs in a wide variety of clinical settings. In the perioperative period, pneumomediastinum is caused by various anesthetic and surgical complications, but may appear spontaneously. When pneumomediastinum occurs with no apparent cause, it is referred to as a spontaneous pneumomediastinum. The suggested mechanism of spontaneous pneumomediastinum is rupture of marginal alveoli due to increased intraalveolar pressure and dissection of air along the bronchovascular sheath into the mediastinum. Predisposing factors include raised intrathoracic pressure, as with coughing, vomiting, and Valsalva maneuvers. The auther's case is presented of pneumomediastinum, with subcutaneous emphysema, pneumoperitoneum, and pneumoretroperitoneum, occurring one day postoperatively, in a 26-year-old female patient who underwent nephrectomy under general anesthesia. The patient was treated conservatively with oxygen and had an uneventful recovery. The authors discuss the possible causes and its management with a review of the relevant literature.