A bronchial artery aneurysm (BAA) is uncommon and usually associated with chronic inflammatory lung disease or a systemic vascular condition, which is rarely the etiology of mediastinal hemorrhage. A middle-aged person presented with spontaneous hemothorax and hemomediastinum. A diagnostic evaluation identified a bronchial artery aneurysm as the source. To prevent further rupture, we performed a bronchial artery embolization. In the absence of trauma or other causes for hemothorax and mediastinal hemorrhage, the possibility of a BAA should be considered. A bronchial artery aneurysm can be managed by interventional techniques as well as surgery.