Stenting is an important treatment option for pulmonary artery stenosis (PS) associated with congenital heart disease (CHD). However, no stent has been approved for this indication in Japan, despite negotiation between academia and the regulatory bodies for longer than 20 years. To evaluate efficacy and safety of the CP stent, we performed the first investigator-initiated clinical trial for pediatric interventional cardiology in Japan. This trial was designed as a single-arm, prospective, clinical trial. Patients who had postoperative PS associated with CHD were included. Stenting was attempted in 24 cases and succeeded in 22 cases. The median age of the patients was 11 years (3–36 years) and weight was 38 kg (12–69 kg), while follow-up for 12 months was completed. In all 22 cases, stenting was successful, with a 50% increase in the minimum lumen diameter (MLD) in 86.4% of patients (90% confidence interval, 68.4–96.2%). The mean percent change in MLD was 119.3 ± 52.5%. In two-ventricle repair, the mean percent change in systolic right ventricular/aortic pressure was − 8.5 ± 16.1%, while that of pressure gradient was − 55.9 ± 41.7%. In single-ventricle repair, the percent change in the mean pressure gradient was − 100.0 ± 0%, while that of SaO2 was 1.4 ± 1.7%. No serious adverse events or significant restenosis was reported. The CP stent is highly effective and safe for PS associated with CHD. This study has significant importance in not only scientific but also social considerations.