Mental health complaints present a significant burden to the healthcare system. In the United States, roughly 20% of adults experience a mental health disorder each year. Long-term adherence to traditional pharmacologic and psychiatric therapies is poor; the time commitment, cost, and pharmacologic side effects of therapy can be substantial. Physical activity as an alternative or adjuvant strategy to promote mental health and treat mental illness shows comparable outcomes in depression and anxiety treatment, without negative side effects. Regular exercise provides numerous health benefits but is also an effective strategy for promoting mental health. Participation in regular physical activity can prevent and treat common disorders such as depression, anxiety, and ADHD, promotes better sleep, and improves memory and mood. Modest amounts of exercise can improve one’s sense of well-being and can be a powerful technique to promote and maintain mental health. Providing a clear, succinct prescription for exercise tailored to the patient’s individual needs, health concerns, and fitness allows a physician to promote physical activity as an effective treatment option for mental illness.