The primary objective of this study was to investigate the associations between sport participation and weight status with physical fitness among French adolescents. The secondary aim was to establish sex- and age-specific physical fitness percentiles for French adolescents. The sample comprised 8084 adolescents (4126 boys, 3958 girls), aged 10-14 years. Participants were tested on cardiorespiratory fitness and muscular strength using the following tests: 20-m shuttle run test and handgrip strength test. A questionnaire on organized sport participation was completed. Physical fitness levels were better in boys (P < 0.005). Handgrip strength increased with age whereas 20-m shuttle run performance decreased with age. Overweight and obese adolescents had significantly lower cardiorespiratory fitness levels than their normal-weight peers (P < 0.005), whereas normal-weight adolescents had lower cardiorespiratory fitness than thin adolescents (P < 0.005). Sport participation was higher for boys (57.2% boys vs. 52.8% girls) (P < 0.001). Adolescents who participated in at least one organized sport (either through a club or at school) were fitter than those who did not participate in organized sports (P < 0.005). Adolescents who engaged in organized sports were more active and physically fit than those who did not participate. The fitness benefits of club sports are greater than those provided by school-based sports, highlighting the potential of sports clubs as a key setting for promoting health. What is Known: • Physical fitness is a strong marker of health in children and adolescents. • The last French Report Card highlighted the lack of fitness data and the need for nationwide programs, while showing a significant decline in cardiorespiratory fitness among youth in recent decades.. What is New: • This study reveals that adolescents participating in organized sports have better physical fitness compared to their peers who do not, emphasizing the potential advantages of club sports over school-based activities. • We highlight the need for targeted strategies, particularly for overweight or obese adolescents and girls, to increase participation in organized sports and enhance health outcomes. • The study emphasizes the need to develop policies that improve access to organized sports clubs and expand physical education in schools, aiming to improve CRF in adolescents.