Spontaneous pneumomediastinum is an uncommon disease that is defined as the presence of free air in the mediastinum in the absence of any obvious precipitating cause. This condition occurs as a rare complication of acute exacerbation of asthma. Classic symptoms include retrosternal chest pain, dyspnea and cough, but are not specific. Spontaneous pneumomediastinum complicated by asthma is usually self-limiting and well controlled with conservative management, but this condition can be potentially life threatening. We report a case of 18-year-old woman with asthma who presented with spontaneous pneumomediastinum. The patient was treated conservatively with oxygen and steroid therapy, and her clinical conditions were improved. Spontaneous pneumomediastinum disappeared.