A case of pulmonary artery rupture induced by balloon occlusion pulmonary angiography (BOPA) is reported. A flow-directed pulmonary artery catheter had been inserted for hemodynamic monitoring in a septic shock patient complicated by acute respiratory distress syndrome. To check for pulmonary damage, BOPA was performed immediately after hemodynamic measurement. Just as the hand injection of contrast medium was ending, the patient began to cough and a small amount of hemoptysis was observed. The angiogram showed the extravasation of contrast medium from the distal pulmonary artery to the situation of catheter tip. Pulmonary hemorrhage was controlled with mechanical ventilatory support with 10 cmH2O positive end-expiratory pressure and no specific therapy was required. This complication should be kept in mind and using a power injector to avoid injurious transient high pressure pulse is recommended.