This nationwide study aimed to evaluate health-related quality of life (QoL) experienced by children after tetralogy of Fallot repair and to compare self-reported physical ability with objective exercise performance. This prospective nonrandomized, government-funded multicenter study enrolled 168 patients (70 girls; ages 8-16 years) after tetralogy of Fallot repair at eight German heart centers. Health-related QoL was analyzed by the self-reported KINDL-R quality-of-life questionnaire. The patients' actual exercise capacity was evaluated by a cardiopulmonary exercise test. Health-related QoL and cardiopulmonary exercise capacity were compared with those of an age-matched German standard population. Correlation of health-related QoL with self-estimated physical rating and cardiopulmonary exercise capacity were analyzed. Health-related QoL in children and adolescents after tetralogy of Fallot repair is without limitation. Compared with the standard population, all the items evaluated by the KINDL-R questionnaire showed better or similar values, whereas objective exercise capacity compared with that of the standard population was impaired. Peak oxygen uptake correlated significantly with the physical well-being (p = 0.002) and the total score (p = 0.01) of the KINDL-R questionnaire. Health-related QoL experienced by children and adolescents after tetralogy of Fallot repair is comparable with that of the healthy standard population. However, closer inspection shows that self-estimated physical functioning is significantly overestimated compared with actual exercise capacity. Quality-of-life instruments and exercise tests, therefore, should be used in a complementary manner with children to avoid eventually fatal misinterpretation of patient-estimated physical ability.