Little data are published about right ventricular (RV) growth and function in infants and neonates after balloon pulmonary valvuloplasty (BPV) for critical valvular pulmonary stenosis (PS). We aimed to assess the RV growth and function during 1 year after BPV for critical valvular PS in neonates and infants. A total of 41 infants and neonates with isolated critical valvular PS who underwent BPV from August 2016 to Sep 2018 were enrolled in the study. Complete Echocardiographic examination was performed to all infants before, 1 week, 1 month, 3 months, 6 months, and 1 year after BPV. The RV systolic pressure and transvalvular pulmonary pressure gradient significantly decreased 1 week after BPV and continue to decrease more slowly during the period of follow-up. During follow-up, RV end-diastolic dimension increased significantly, whereas RV anterior wall thickness significantly decreased. The mean diameters of pulmonary valve annulus and tricuspid valve annulus significantly increased after BPV over the period of follow-up. RV systolic and diastolic dysfunction improved significantly as reported by reduced RV Tei index and tricuspid annular systolic velocity and increased RV E/A ratio. RV growth and function were significantly improved after BPV for critical PS in infants and neonates and catch-up growth of right ventricular structures occurred after 6 months of BPV.