Patients with simple shunt lesions, such as atrial septal defect (ASD), ventricular septal defect (VSD) and persistent arterial duct (PDA) remain at risk of developing pulmonary hypertension (PH) even after correction of their cardiac defect. We aimed to assess the contemporary prevalence of PH in a well characterized nationwide group of patients based on the German National Register for Congenital Heart Defects. We included all patients >16 years of age with an isolated diagnosis of ASD, VSD or PDA. Only patients with previous surgical or interventional closure of the defect were included. Patients with genetic syndromes were excluded. Out of 49,597 CHD patients in the register we identified 825 patients with closed, isolated simple defects (52% ASD, 41% VSD, 7% PDA). Of these, 25 (3%) developed PH after a median follow-up of 16 years from defect closure. The risk of PH increased significantly with age at follow-up (p < 0.0001) and age at repair (p < 0.0001) on logistic regression analysis Patients with PH were significantly more likely to be symptomatic (59% vs. 9% in NYHA class ≥2, p < 0.0001) and had significantly higher mortality (hazard ratio 13.4, p < 0.0001) compared to the remaining patients. Based on data from the German National Register CHD Register we report a PH prevalence of 3.0% in patients with corrected, simple lesions. Patients with PH were more symptomatic and had significantly increased mortality risk. Life-long surveillance and low threshold for workup is recommended to ascertain diagnosis of PH, which has important prognostic and clinical implications. •Pulmonary hypertension (pH) is common in congenital heart disease.•Simple corrected lesions have increased life-long risk of developing PH.•The risk of developing PH ranges between 3 and 5% and increases with age.•Even minor shunt lesions warrant life-long follow-up and screening for PH.