Introduction: This cross-sectional study evaluated the healthy, active lifestyle capacity (daily physical activity, strength, flexibility, body composition) of children after Fontan, which was hypothesized to be lower than healthy peers. Methods: Participants (n=64, 25 female) were 9 ± 2 years of age. Fontan completion occurred at 3 ± 1 years of age. Canadian Health Measures Survey protocols assessed aerobic endurance (walking up/down steps at set pace), strength (handgrip dynamometry), flexibility (sit and reach), body composition (body mass index) and daily moderate-to-vigorous physical activity (7-day accelerometry). Participant versus published norm differences were evaluated with t-tests. Linear regression evaluated associations with age/gender/demographic factors. Results: Children after Fontan had strength scores similar (mean difference 1 kg) to their peers, were less likely to be obese (mean difference of body mass index = 1.1 ± 2.5, p=.001) and performed 50 minutes of moderate-to-vigorous activity per day. Estimated maximal aerobic endurance (mean difference = 21 ± 3 ml/kg/min or 61% of expected) and flexibility (mean difference = 9 ± 8 cm or 64% of expected) were lower than peers(p<.001). Participants performed fewer minutes of daily activity (mean difference from normal 12 ± 17 minutes/day, p<.001), but almost all (60/63) demonstrated the capacity for at least 20 minutes per day. Daily activity was higher with Fontan completion at a younger age (4 ± 2 mins/year) and for those taking antithrombotic medication (7 ± 18 and 22 ± 17 fewer minutes/day for those taking/not taking antithrombotics, respectively). Conclusions: Children after Fontan demonstrate the capacity to successfully perform the daily physical activity associated with optimal health. They have similar levels of strength and good body composition. We recommend that children after Fontan be counselled to expect that they can successfully participate in physically active peer play.