**Abstract**

Mental health conditions are a major public health issue affecting many people worldwide. Evidence suggests that physical activity and exercise can prevent and treat mental health conditions, especially depression and anxiety. Several mechanisms are involved in the relationship between mental health conditions and exercise, from neurobiological to behavioural mechanisms. This chapter intends to explain the main mechanisms that explain that interaction and present recent evidence from studies that analyse the effects of exercise on mental health outcomes. It also highlights the principles of physical exercise (frequency, intensity, volume, and type) and how they can influence the main outcomes of mental health. Engaging in regular physical activity may prevent the onset of different mental health disorders. Also, evidence shows that exercise diminishes depressive symptoms. This chapter is indicated for health professionals who wish to have a broad view of the relationship between exercise and mental health. This knowledge can be valuable in designing public interventions that aim to treat mental disorders and optimise mental health.

**Keywords:** depression, anxiety, lifestyle, physical activity, mental health conditions
