We report an adult case of accessory cardiac bronchus (ACB) which extended from the carina to the diaphragm. A 32-year-old woman, with a history of frequent respiratory infections since childhood, recently presented with bloody sputum, and was admitted to our hospital. The ACB was detected as a supernumerary bronchus diverging from tracheal bifurcation. Complete resection of the ACB was performed by video-assisted thoracic surgery via minithoracotomy, approaching from the 5th intercostal space. The bloody sputum was caused by chronic inflammation of the ACB. She has been asymptomatic since surgery.