The objective of this study was to assess the mid-term results of mitral valve (MV) repair in infancy and childhood with isolated mitral regurgitation (MR). From January 2005 to January 2016, 40 consecutive patients with isolated MR underwent MV repair in Fuwai Hospital, Beijing, China. Patients’ clinical data were analyzed retrospectively. Mean age at operation was 13 ± 5 (6–24) months and 22 patients (55%) were younger than 1 year. Mean weight at operation was 8.5 ± 1.9 (4.2–13) kg and 34 patients (85%) were lighter than 10 kg. All patients presented moderate or greater MR. After MV repair, all patients had mild MR or none, while two patients underwent re-repair immediately when TEE showed moderate MR. Mean left atrial diameter decreased from 28.0 ± 6.5 to 20.7 ± 4.8 mm and mean left ventricular end-diastolic diameter decreased from 38.6 ± 7.0 to 30.2 ± 4.9 mm (p < 0.001 for both). There was no early death. Clinical follow-up was conducted in 37 patients over an average period of 49 ± 31 (20–134) months. Follow-up echocardiography showed that one patient had severe MR who underwent redo repair 14 months after operation, one patient had moderate to severe MR, and three patients had moderate MR. Overall freedom from moderate or greater MR was 96.3 ± 3.6%, 91.9 ± 5.5%, and 83.6 ± 9.4% at 2, 5, and 10 years, respectively. The early and mid-term results of MV repair in pediatric patients with isolated MR were satisfactory. In majority of patients, less complex surgical repair techniques were utilized, namely annuloplasty or commissuroplasty. The combination of various repair methods in complex patients could achieve excellent outcome.