A 79-year-old woman with Bland-White-Garland syndrome was admitted to our institution for surgical treatment of severe mitral regurgitation (MR). She had previously undergone mitral valve repair and coronary artery bypass grafting for both mitral insufficiency and a coronary artery anomaly 14 years earlier. However, the degree of residual MR had gradually worsened, and redo mitral valve surgery was scheduled. Multidetector row computed tomography revealed that the right coronary artery (RCA) was dilated and located just behind the sternum, and saphenous vein graft bypassed to the left anterior descending artery was occluded. This meant that the RCA was the only vessel supplying coronary blood flow. We successfully performed port-access mitral valve replacement under mild hypothermia with fibrillatory arrest to prevent damage to the RCA. We propose that port-access surgery is a safe and effective treatment for redo cardiac surgery after initial surgical correction of a congenital heart anomaly.