Background: Pulmonary hypertension is a significant yet rare disease that can have many long-term consequences, including death. Cardiac catheterization is the gold standard for measuring pulmonary artery mean pressures (PAMP), but is invasive and risks potentially serious complications. This study aimed to create a semi-quantitative, non-invasive measure of PAMP using septal positioning. Methods: This study was a retrospective study of patients with and without pulmonary hypertension who had a transthoracic echocardiogram and cardiac catheterization. Patients undergoing atrial septal defect closure represented controls. Two blinded readers calculated the “Echocardiographically-Derived Septal Positional Angle (EDSPA)” which was compared to corresponding catheterization data including mean pulmonary artery pressures. Results: A total of 159 children were included, of which 151 had useable echocardiographic data. 40 children were identified as having pulmonary hypertension while 111 children had an atrial septal defect. Patient age ranged from a minimum of 54 days and maximum of 19 years [mean 7.1 years (SD=5.30)]. Inter-observer variability between two readers [Pearson correlation coefficient of 0.939 (p <0.001)] and intra-observer variability were low [intraclass correlation coefficient (ICC) of 0.95 and 0.96 for each observer respectively]. An EDSPA of ≤39° predicted a PAMP>20 mmHg (as measured by cardiac catheterization) with a 76% sensitivity and 76% specificity (AUC 0.846). Conclusions: EDSPA is a useful, non-invasive, and reproducible echocardiographic measure of PAMP that is easy to perform. With a sensitivity and specificity near 80%, it has significant utility in screening for pulmonary hypertension and determining which patients should undergo further invasive diagnostic testing.