Little information exists on left atrial (LA) function in healthy children and in patients with congenital aortic valve stenosis (AS). We sought to determine whether patients with significant congenital AS have detectable abnormalities in LA size and function compared with matched normal controls. Retrospective chart review and analysis of 2-dimensional echocardiographic images for phasic left atrial volumes (LAVs) and longitudinal LA strain by speckle tracking in children ≥1 years of age with ≥ moderate isolated congenital AS. LAVs and LA strain in AS cases were compared with age, gender, and body surface area-matched controls (healthy children with a normal echocardiogram). Between June 2004 and October 2012, there were 36 eligible AS cases [age 13 (range 3 to 27) years; 30 males] with a median maximal Doppler gradient of 63 (range 43 to 94) mm Hg. No significant interobserver and intraobserver differences were noted in the analyses of normal subjects. Significantly higher phasic body surface area-adjusted LAVs [preatrial contraction: p = 0.01; minimal: p = 0.04] and higher LA contractile function parameters [indexed active LA stroke volume: p = 0.03; peak negative strain p = 0.04] were noted in AS cases compared with matched controls. In conclusion, compared with normal, children with congenital AS have higher preatrial contraction and minimal phasic LA volumes and higher LA contractile function.