The World Health Organization defines mental health as a state of wellbeing whereby individuals are able to realize their potential, cope with the normal stresses of life, work productively, and make contributions to their communities. Organized sport may provide a unique and engaging vehicle through which to promote mental health among children. The positive association between participation in organized sports and mental health during childhood has been consistently demonstrated. A recent meta-analysis found that children who participated in exercise programmes that exceeded 60 minutes showed significant improvements in overall mental health compared to those who participated in shorter duration programmes. The application of self-determination theory (SDT) within sport has received considerable attention. Positive relationships with social agents in youth sport can have important implications for the wellbeing of children who participate in sport.