Approximately10-20% of children and youth are diagnosed with a mental disorder and many more experience subclinical symptoms. With increasing prevalence rates, researchers are attempting to identify modifiable behaviours that can prevent symptoms related to mental disorders. Increasing physical activity has been identified as an important target to enhancing mental health. Despite decades of research showing the benefits of physical activity, rates of physical activity are decreasing, with some suggesting that increased screen time has displaced time spent in physical activity. In this presentation, I will review the literature and my own research that has examined links between physical activity and mental health, with a brief discussion on screen time and mental health. I will also discuss factors related to better quality engagement in physical activity and screen time and their links to mental health.