Background: Adults presenting with an unrepaired atrial septal defect and pulmonary arterial hypertension (ASD-PAH) are typically classified as “correctable” or “non-correctable”. The use of directed PAH medical therapy in non-correctable ASD-PAH leading to favorable closure candidacy, repair status and long-term follow-up is not well studied. We therefore sought to characterize response to PAH targeted therapy in ‘non-correctable’ ASD-PAH. Methods and results: Nine North American tertiary care centers submitted retrospective data from adults with unrepaired ASD-PAH that did not meet recommendations for repair at initial presentation (1996–2017). Sixty-nine patients (women 51(74%), 40 ± 15 years, mean pulmonary artery pressure (mPA) 51 ± 13 mm Hg, pulmonary vascular resistance (PVR) 8.7 ± 4.9 Wood units, Qp:Qs 1.6 ± 0.4) were enrolled. All patients were prescribed PAH targeted therapy and late shunt repair occurred in 19(28%) (Women 15(29%) vs. Men 4(22%), p = 0.6). At late follow-up (4.4 ± 2.9 years) 6-minute walk test distance (6MWTD) was significantly better in the group that underwent repair (486 ± 89 m vs. 375 ± 139 m, p < 0.05). Transthoracic echo showed significant improvement in right ventricular (RV) function (severe dysfunction in repaired 8(40%) vs. unrepaired groups 35(69%), p < 0.05). Divergent survival curves suggest that with larger studies and more follow-up, differences in survival between repaired and unrepaired groups may be important. (repaired: 17(94%) vs. unrepaired: 32(81%), p = 0.18). Conclusions: This is the first and largest multicenter study evaluating the “treat-to-close” approach in non-correctable ASD-PAH. Our new data supports further study of this strategy in patients who have reversibility of PAH in response to targeted therapy. We demonstrate that in the carefully selected patient with non-correctable ASD-PAH, successful shunt repair is possible if post-therapy PVR is ≤6.5 Wood units. Patients who underwent repair had improved RV function following PAH targeted therapy. Divergent survival curves suggest that with further study, defect repair may affect medium-term to late survival.