Pneumomediastinum is defined by the presence of air in the mediastinum, which may be either secondary to trauma, pneumothorax or perforation of the airways, or spontaneous. We report the case of a 28-year-old female patient with pneumomediastinum revealing asthma in acute exacerbation. The patient wasn't known to be asthmatic or to have an atopic background, no history of surgery, nor any notion of trauma, or recent iatrogeny. She presented with sudden onset of tachypnea associated with chest tightness and productive cough with greenish sputum. Auscultation of her chest revealed audible sibilant rales with the presence of subcutaneous emphysema. Chest radiograph objectivated an aeric border along the edge of the cardiac silhouette associated with subcutaneous hyperclarity of the cervical region. The thoracic CT scan confirmed the presence of a diffuse moderate pneumomediastinum. The patient was put under nasal oxygen, nebulized Ventolin and given intravenous corticosteroid therapy. The patient evolved favorably within three days marked by clinical improvement, the persistence of discrete sibilant rales at the apexes, as well as subcutaneous emphysema in regression after oxygen therapy and conventional medical treatment.