Optimal mitral valve operation requires adequate exposure without impairment of atrial physiology, namely sinus node and atrioventricular node function. We used an extended vertical transseptal atrial approach in 34 consecutive patients. The extended vertical transseptal approach combines two semicircular atrial incisions circumscribing the tricuspid and mitral annuli anteriorly and superiorly, allowing exposure of the mitral valve by deflecting the ventricular side using stay sutures. The right atrium is opened anteriorly along the atrioventricular sulcus. The atrial septum is incised vertically through the fossa ovalis. The right atriotomy is extended superiorly in the right coronary fossa between the right atrial appendage and the atrioventricular sulcus to meet the septal incision. The two joint incisions are extended onto the left atrial roof transversely. At this point, the two semicircular incisions are performed and joined, and mitral valve operation is performed. There were 18 women and 16 men. Five patients had ischemic mitral valve regurgitation, 18 had mitral valve prolapse, and 11 had rheumatic heart disease. The mitral valve was replaced in 17 patients and repaired in 17. There were no perioperative complications associated with the atriotomies, ie, no bleeding, no atrioventricular nodal dysfunction, and no sinus node dysfunction. The extended vertical transatrial septal approach provides good mitral valve exposure without inherent complications.