We aimed to evaluate the outcome and regional and global left-ventricular (LV) function after aortic valve repair in children with congenital aortic valve disease. Thirty-two consecutive patients with a mean age of 12.62 years (4 months to 18 years) undergoing aortic valve repair due to valve stenosis (AS group, n = 21) or aortic regurgitation (AR group, n = 11) were studied during a follow-up period of 12 months regarding change and adaptation of myocardial function using conventional and novel echocardiographic methods, including two-dimensional (2D) strain echocardiogram. Conventional and 2D strain echocardiographic studies were performed and analyzed off-line using commercially available software (EchoPac 6.1.0, GE). Peak aortic valve gradient decreased from 62.04 ± 30.34 mmHg before surgery to 22.80 ± 14.13 mmHg 2 weeks after surgery and to 35.73 ± 22.11 mmHg 12 months after surgery (p = 0.01). The degree of AR decreased significantly to grade 0 in 20 children and to grade I in 12. There was a significant decrease of thickness of the interventricular septum (IVS) and posterior wall resulting in improvement of LV mass index (p = 0.007, p = 0.043, and p = 0.001, respectively). Significant decrease of myocardial thickness was found, especially in the IVS, in the AS group (p = 0.008), and a significant decrease in LV end-diastolic dimension (EDD) was found in the AR group (p = 0.007). 2D strain analysis showed that global peak strain, global systolic strain rate, and global early diastolic strain rates improved significantly for all patients during the study period after aortic valve repair (p < 0.001, p = 0.037, and p = 0.018, respectively). The global strain and strain rates correlated significantly to IVS thickness (r = 0.002 and r = 0.003, respectively), LV mass index (r = 0.02 and r = 0.015, respectively), and EDD (r = 0.26 and r = 0.005, respectively). Aortic valve repair surgery in pediatric patients results in improvement of global and regional systolic and diastolic LV parameters, which was better shown by 2D strain parameters rather than conventional echocardiographic parameters.