Retroaortic left renal vein occurs infrequently and poses potential hazards to the surgeon during abdominal aortic surgery. We herein report the case of a 77-year-old man with a retroaortic left renal vein who underwent an abdominal aortic aneurysm (AAA) repair. The retroaortic left renal vein was diagnosed preoperatively by contrast-enhanced computed tomography (CT). The patient underwent a successful abdominal aortic replacement with an uneventful postoperative course without any renal complications. The CT scan was useful for both evaluating the AAA and for establishing the presence of the venous anomaly. Major venous anomalies (retroaortic left renal vein, left renal vein collar, left-sided inferior vena cava, and caval duplication) should thus be taken into consideration in AAA operations.