This study aimed to assess whether sex moderates the association of fundamental movement skills and health and behavioral outcomes. In 170 children (10.6 ± 0.3 years; 98 girls), path analysis was used to assess the associations of fundamental movement skills (Get Skilled, Get Active) with perceived sports competence (Children and Youth--Physical Self-Perception Profile), time spent in vigorous-intensity physical activity, sedentary time, and body mass index z score. For boys, object control skill competence had a direct association with perceived sports competence ([beta] = 0.39; 95% confidence interval, CI [0.21, 0.57]) and an indirect association with sedentary time, through perceived sports competence ([beta] = -0.19; 95% CI [-0.09, -0.32]). No significant association was observed between fundamental movement skills and perceived sports competence for girls, although locomotor skills were found to predict vigorous-intensity physical activity ([beta] = 0.18; 95% CI [0.08, 0.27]). Perceived sports competence was associated with sedentary time, with this being stronger for boys ([beta] = -0.48; 95% CI [-0.64, -0.31]) than girls ([beta] = -0.29; 95% CI [-0.39, -0.19]). The study supports a holistic approach to health-related interventions and highlights a key association of perceived sports competence and the time children spend sedentary.