In pediatric patients, mitral valve (MV) repair is preferable than MV replacement because of no need for anticoagulation and its feasibility in small children. However, long-term outcome of MV repair is still unclear. In the present study, fifty-two pediatric patients who underwent MV repair (n = 46) and MV replacement (n = 6) against mitral regurgitation (MR) between January 1970 and December 1996 were evaluated. 46 patients had associated diseases. Mitral annuloplasty was applied in 20 patients (by Kay method (n = 14) and Paneth-Burr method (n = 6) before and after 1991, respectively). Freedom from reoperation rate in patients with partial endocardial cushion defect (ECD) was significantly lower than that in other patients after MV repair, which was significantly higher than that in patients with MV replacement. Diameter of mitral annulus grew within normal range after MV repair. In conclusion, MV repair may provide better outcomes with respect to reoperation and growth of MV in pediatric patients except with partial ECD.