Pulmonary hypertension (PH), defined as mean pulmonary arterial pressure ≥25 mm Hg, may be a complication of a secundum atrial septal defect (ASD). This study sought to evaluate the impact of PH at time of ASD device closure on patient survival. A prospectively collected database of ASD closures was utilized. Patients were stratified by age above and below the cohort median (48 years). Survival was analyzed by preprocedural PH status, age cohort, and echocardiographic resolution of PH at 3 months postdevice closure. PH was present in 48 of 228 patients (21.1%) and was more common in the older cohort (31.3% vs 10.6%, p <0.01). ASD size was unrelated to the presence of PH (p = 0.33). Older patients had more medical co-morbidities including diabetes (p = 0.02), hyperlipidemia (p <0.01), and systemic hypertension (p <0.01) compared with younger patients. PH did not impact survival in patients ≤48 years, but PH was associated with fivefold increased risk of death in patients >48 years (p < 0.01). Patients with preprocedural PH and RVSP ≥40 mm Hg at 3-month follow-up continued to have an increased risk of mortality (p <0.01), whereas those with resolution of PH had similar survival to those without PH at time of closure. In conclusion, PH is common in adults with unrepaired ASDs and appears unrelated to defect size. PH in older adults and its persistence closure are strong predictors of a worsened clinical outcome. These patients may benefit from additional risk assessment and advanced medical therapies to mitigate this risk.