A 74-year-old woman who had had severe mitral regurgitation (MR) due to dilated cardiomyopathy (DCM) was referred to our hospital for surgical management because she had suffered from congestive heart failure (CHF) of NYHA functional class IV in spite of maximal medical treatment. We have successfully performed mitral annuloplasty (MAP) using a Carpentier annuloplasty ring. Her postoperative course was good and her symptom improved to NYHA functional class II to III one year after the operation. However, the left ventricular functional improvement was minimal. The regurgitant fraction decreased from 0.62 to 0.11 after the operation but the left ventricular ejection fraction also decreased from 0.26 to 0.11. We had an impression that MAP could be considered as one of the procedures for severe MR due to DCM, if CHF was not controlled by any medications.