Cardiovascular manifestations of acromegaly include cardiomegaly and very often hypertension, coronary atherosclerosis, and diabetes. Primary valvular disease is less commonly observed. A 62-year-old woman had acromegaly associated with mitral regurgitation (MR) resulting from prolapse of the posterior mitral leaflet, which was successfully repaired. At the age of 57 years, the patient was admitted due to heart failure without valvular disease. Acromegaly was diagnosed and a pituitary tumor was removed surgically. At the age of 62, a heart murmur was found, and moderate to severe MR was diagnosed. MR was successfully corrected by quadrangular resection of the posterior leaflet, including the prolapsed portion, and prosthetic ring annuloplasty. Histological examination showed myxomatous degeneration. The patient recovered uneventfully. During the last 2 decades, only 21 surgical cases of valvular disease associated with acromegaly were reported in the literature; mitral valve lesions in 10 patients (all with regurgitation), aortic valve lesions in 10 patients (7 with regurgitation and 3 with stenosis), and one with combined lesions of mitral and aortic valves. Since histology did not show specific changes in many reports, it is still unclear whether valve lesions are caused by a high GH hormone level. Although mitral valve replacement was recommended in the 1990s due to the fragility of valvular rings and their apparatus, mitral repair was performed in 5 recent cases and no recurrence has been reported.