Left bronchial isomerism is a rare condition characterized by a bronchial structure on the right side that is a mirror image of the left side. In this report, we record our experience with a 62-year-old female lung cancer patient in whom left bronchial isomerism was discovered during surgery using a thoracoscope. A right upper pulmonary lobectomy was successfully completed, the key to which was successful separation of the right upper and middle lobes. As there is a risk of excising the wrong bronchi in such cases, thoracic surgeons need to identify bronchus variations. The optimal method to do this is to use a bronchoscope and computed tomography images of the bronchial tree reconstruction prior to surgery.