Klippel-Feil syndrome, characterized by congenital fusion of any 2 or more cervical vertebrae, is a rare disorder in which skeletal and other organ system-related abnormalities have been reported. This article reports a case of mitral valve regurgitation in a patient with Klippel-Feil syndrome and related thoracic deformity who underwent mitral valvuloplasty. Postoperatively, the mitral valve regurgitation disappeared, and there has been no recurrence for 3 years. This case highlights mitral valvuloplasty via median sternotomy as an excellent treatment for mitral valve regurgitation in a patient with thoracic deformity related to Klippel-Feil syndrome.