The wide-ranging benefits of physical activity for consumers with mental illness are acknowledged within the mental health nursing field; however, this is not commonly translated to practice. The primary aim of this paper is to argue that mental health nurses are well positioned to, and should, provide leadership in promoting physical activity to improve the quality of care for people with mental illness. Topics addressed in this paper include the relationship between physical activity and both physical and mental health, the views and experiences of consumers with physical activity, the efficacy of physical activity interventions, the attitudes of nurses to physical activity as a component of care, barriers to a physical activity focus in care for mental illness, and the role of mental health nurses in promoting physical activity. There is a clear and important relationship between physical activity and mental health. Mental health nurses are well positioned to encourage and assist consumers to engage in physical activity, although they might lack the educational preparation to perform this role effectively.