Objective: This study aimed to investigate the safety, tolerability, and efficacy of selexipag in children and young adults with idiopathic and heritable pulmonary arterial hypertension. Methods: This retrospective cohort study included clinical data from five children and six young adults with pulmonary arterial hypertension receiving selexipag as add-on therapy or as a transition from beraprost sodium or epoprostenol infusion therapy. Clinical efficacy was evaluated by measuring improvement in clinical variables from baseline, including hemodynamic parameters. Results: Of the 11 patients, 6 were switched from beraprost sodium to selexipag and one paediatric patient transitioned from epoprostenol to selexipag. The median maintenance dose of selexipag in children was 80 mu g/kg/day. In nine patients undergoing repeat catheterisation, statistically significant improvements were observed after the initiation of selexipag in terms of mean pulmonary arterial pressure (p < 0.01), pulmonary vascular resistance index (p < 0.05), and cardiac index (p < 0.01). None of the patients had clinical worsening after selexipag during follow-up, but one young adult patient discontinued treatment due to severe headache. The most common side effect profiles were headache, nausea, abdominal pain, jaw pain, myalgia, and diarrhoea. Conclusions: Selexipag may have a favourable safety profile and potential efficacy in children and young adults with pulmonary arterial hypertension.