The anatomical abnormalities of the pulmonary veins may have a serious impact on complications that may arise during pulmonary lobectomy. We present a surgical case of left lung cancer in a patient, who was a 69-year-old male, with the left superior and inferior pulmonary veins forming a common trunk outside the pericardium. In this present case, because of extensive adhesions, incomplete lobulation, and tumor infiltration of the main pulmonary artery, we could not identity the common trunk with certainty before excising the left upper lobe. Although this patient was fortunately discharged without complications, there was no choice but to perform pneumonectomy because of the interruption of the inferior pulmonary vein. Retrospectively, the preoperative CT films showed the anatomical anomalies involving the pulmonary veins. However, since the length of the common trunk outside the pericardium was short and the inferior pulmonary vein was thinner than usual and its venous distribution conformed to a normal structure, the anatomy appeared normal. In excising the pulmonary lobe, it is mandatory to ascertain the distribution of the vascular system prior to surgery.