The prevalence of pneumothorax cases among Intensive Care Unit patients who require mechanical ventilation ranges from 4%-15%. A pneumothorax remains one of the most serious complications of positive pressure ventilation. It can be diagnosed in a critically ill patient through a physical examination or radiographic studies that include chest radiographs, ultrasonography, or computed tomography scanning. However, in a critically ill patient, the diagnosis of a pneumothorax is often complicated by other diseases and by difficulties in imaging sick and unconscious patients. Although electrocardiogram changes associated with a pneumothorax have been described for many years, there has been no report of such among patients who require mechanical ventilation. In this paper, we report 2 cases of a spontaneous pneumothorax with paroxysmal supraventricular tachycardia in patients who required invasive mechanical ventilation due to acute respiratory failure.