The exercise capacity and limitation in children with asymptomatic atrial septal defect (ASD) have not been explored thoroughly. The aim of our study was to examine the influence of asymptomatic ASD on exercise capacity in children. Fifty children with asymptomatic ASD who had undergone medical interventions at least 4 years ago and fifty normal children were recruited in this study. The exercise capacity was assessed by the symptom-limited exercise test through the Bruce treadmill protocol. The pulmonary function was also evaluated by the spirometry. Circulatory and ventilatory impairments were respectively reflected by chronotropic incompetence (CI) and ventilatory limitation as measured by the exercise test and spirometry. Eleven (22%) of children with ASD failed to reach the age-predicted peak heart rate during the exercise test. Also, children with ASD had significantly lower oxygen consumption at anaerobic threshold and peak exercise (P < 0.01). The rate of circulatory impairment was significantly higher in children with ASD (P < 0.01). However, the pulmonary function and ventilatory limitation were comparable between these two groups. Within the ASD group, children with CI had significantly worse peak oxygen consumption than their peers without CI (P < 0.01). Our study examined a larger population sample and confirmed that children with asymptomatic ASD, who had previously undergone medical interventions, had significantly worse exercise capacity than normal children. This difference in exercise capacity was mainly related to circulatory impairment. Our findings support the concerns of exercise limitation in ASD children.