<p>Patients with Fontan circulation have difficulty achieving normal peak oxygen consumption (VO2_peak) during cardiopulmonary exercise testing (CPET). Exercise performance wanes over time and has an established association with increased morbidity in adult patients with a Fontan. Our study aimed to identify clinical factors associated with normal aerobic capacity in pediatric patients with a Fontan. Retrospective chart review was performed on 41 patients, 6 to 18 years old, who underwent extracardiac Fontan palliation. Patients who did not meet satisfactory test criteria by achieving respiratory exchange ratio (RER) &gt; 1.0 or peak heart rate &gt; 85% predicted were excluded. Clinical factors included ventricular dominance, age at Fontan, body mass index (BMI), degree of atrioventricular (AV) valve regurgitation, history of regular activity (3 or more days per week of exercise), and participation in recreational or competitive sports. CPET data was reviewed for each patient, with normal performance defined as VO2_peak &gt; 80% predicted.35 patients met inclusion criteria. 12 patients achieved a normal VO2_peak. Analysis of variance and chi-squared tests were used to investigate associations between achievement of normal VO2_peak and the clinical factors. History of regular physical activity and participation in recreational or competitive sports were significantly associated with a normal VO2_peak (<i>p</i> = 0.029 and 0.01 respectively). No significant association was found between normal VO2_peak and other clinical factors such as BMI, ventricular dominance, degree of AV valve regurgitation, or pre-exercise spirometry. Regular exercise and participation in sports were associated with normal aerobic capacity in our patients with Fontan circulation. These findings add to the growing body of evidence suggesting that regular physical activity is beneficial to pediatric patients with a Fontan.</p>