We compared the endothelial function and vascular wall characteristics of 11 children with tetralogy of Fallot (TOF) (age 13 ± 3 years) with the characteristics of 17 age-matched peers (12 ± 2 years). Echocardiographic Doppler measurements were performed under standardized conditions to assess (1) the carotid and femoral artery diameter and intima–media thickness, (2) brachial artery endothelial function using flow-mediated dilation, and (3) central and peripheral compliance using pulsewave velocity. In addition, the physical activity level was assessed using a validated questionnaire. We found that the physical activity level of the children with TOF was lower than that of the controls, but the difference did not reach statistical significance (4.5 vs 5.9 h/wk, p = 0.087). A significantly larger femoral artery intima–media thickness was observed in those with TOF, and the carotid and brachial artery diameter and intima–media thickness were comparable between groups. The children with TOF demonstrated a significantly lower brachial artery flow-mediated dilation than that of the controls. The central and peripheral compliance did not differ between the 2 groups. In conclusion, children with TOF demonstrated an impaired brachial artery endothelial function and increased intima–media thickness of the femoral artery compared to their healthy peers. In conclusion, our findings have, therefore, indicated that children with TOF, already at a young age, have changes in vascular function and structure.