Mitral regurgitation caused by papillary muscle rupture has a poor prognosis and should be operated on soon after onset. We recently encountered a patient who was operated on 8 months after the onset of mitral regurgitation caused by rupture of the posterior papillary muscle. The patient was a 72-year-old man who was admitted as an emergency case for acute left heart failure due to severe mitral regurgitation. As medical treatment was effective, he refused to have mitral valve surgery. Six months later, he was admitted to our hospital complaining of nocturnal orthopnea and underwent surgical treatment. Severe mitral regurgitation with postero-medial papillary muscle rupture was revealed by transesophageal echocardiography. Coronary angiography showed 90% stenosis of the proximal left circumflex artery. At 8 months after the onset of mitral regurgitation, the patient underwent successful scheduled mitral valve replacement together with coronary artery bypass grafting. There are few reports of mitral valve surgery being performed successfully for papillary muscle rupture due to coronary artery disease in the chronic stage.