Patients with coarctation of the aorta (CoA) have increased left ventricular (LV) afterload that has been shown to impact the LV and ascending aortic function. We aimed to examine the effect of coarctation on LV function and aorto-septal angle (AoSA) before and after surgical repair. We retrospectively studied 21 patients with surgically repaired CoA at a median age of 9 (2-53) days at three time points: (1) just before intervention, (2) at short-term follow-up, and (3) at medium-term follow-up after intervention. AoSA was measured from the parasternal long axis view, at three time points during the cardiac cycle: (1) end diastole, (2) beginning of systole, and (3) at peak ejection in the descending aorta. In addition to conventional LV structure and function, global longitudinal strain, and strain rate were measured using STE technique and Tomtec software. Three groups of age matched healthy children served as controls at each time point. AoSA was significantly wider before intervention, in particular at peak ejection in the descending aorta (144° ± 6.4° vs. 136° ± 4.1°; P < .0001), and correlated with CoA pressure gradient. After intervention, AoSA normalized and significantly correlated with the increase of LV cavity function and overall LV deformation parameters. AoSA is abnormally wide in neonates with CoA and is associated with severity of obstruction, LV dysfunction and compromised LV global deformation.