Background: Subcutaneous treprostinil is recommended as add-on therapy in high-risk patients with pulmonary arterial hypertension (PAH), but there are few data on its use and outcome in children. Methods: Retrospective observational study. Medical records from paediatric patients diagnosed with PAH during the last 10 years were reviewed. We evaluated safety and outcome of patients treated with subcutaneous treprostinil. Results: We identified 10 patients (5 girls) with PAH who initiated treatment with treprostinil between 2011 and 2017: 6 with idiopathic PAH and 4 with PAH related to congenital heart disease. Median age at diagnosis was 1.8 years (0.1-7.8). All patients were in functional class III when they started treprostinil after a median of 3.3 years (0.3-11) since the diagnosis, and all were on oral combined therapy and inhaled iloprost. Treprostinil was gradually increased while iloprost was downtitrated. At 3 months: 5 patients improved and 5 stabilized; median reduction of brain-type natriuretic peptide levels was 83% (7/10 patients); all showed persistent right ventricle dysfunction with significant enlargement. Treprostinil median maximum dose was 68 ng/Kg/min (32-100), median duration was 11 months (2-26). Side effects included local pain, erythema and cellulitis (2/10), although well tolerated without stopping the treatment. Outcome: 4 continued on treprostinil and oral therapy, 2 transitioned to epoprostenol, 6 received a lung transplant (including 2 on epoprostenol). Two died due to post-transplant complications. Conclusions: Subcutaneous treprostinil can improve or stabilize high-risk PAH children with few side effects, being well accepted by them and their families.