Aortic dissection with extensive involvement of other branching vessels is a serious concern and has a grave prognosis. Although its occurrence is rare, vessel dissection can extend from the ascending aorta to the pulmonary artery because they share a common vessel adventitia and this can result in pulmonary artery intramural hematoma or pulmonary artery dissection, with blood leakage into the pulmonary alveoli. Herein, we report a case of Stanford type A aortic dissection with suspected involvement of the pulmonary artery, which contributed to an extensive pulmonary hemorrhage as revealed by computed tomography. Furthermore, left ventriculography revealed subsequent enhancement of the bilateral pulmonary arteries, thus yielding additional support to the notion that this complication can occur in patients with type A aortic dissection. In addition to a dissected vessel flap and intramural hematoma over the pulmonary artery, extensive pulmonary hemorrhage that results from unstoppable blood leakage into vulnerable lung alveoli may be an indirect but significant clue for potential concomitant pulmonary artery intramural hematoma or dissection.