A 75-year-old man was referred for treatment of mitral valve prolapse secondary to tendon rupture. He had been receiving oral and inhaled corticosteroids for bronchial asthma and bronchial ectasia. Chest X-ray showed cardiomegaly with protrusion of the right atrium shadow. Computed tomography revealed dislocation and counterclockwise rotation of the heart with the apex of the heart located in the mid-thorax, indicating mesocardia. We believed that it would have been difficult to expose the mitral valve through a right-sided left atrial approach. Thus, we planned to perform mitral valve repair via a trans-septal approach. The right thoracotomy approach was not suitable because of respiratory dysfunction. After a median sternotomy, the left anterior descending coronary artery was identified just beneath the midline of the sternum. Even after decompression of the heart under cardiopulmonary bypass, we could not obtain a good view of the right side of the left atrium. By a transseptal approach with a self-retaining retractor and atrial hooks, we obtained adequate exposure of the mitral valve and performed the mitral valve repair uneventfully.