Exercise or physical activity is considered as medicine, and both have several positive effects, which outweigh largely the risks. For older adults with mental health issues, physical activity and exercise might be even more important than for healthy people: exercise and physical activity can prevent or at least delay the onset of some mental disorders; they have therapeutic effects, either as the sole intervention or as an adjunct treatment for mental disorders. Patients are more likely to recover from a mental illness if they are regularly physically active. It is recommended for older adults to be physically active for at least 150 min per week at moderate intensity or for at least 75 min at vigorous intensity. Exercise adherence is quite low, and measures to improve exercise adherence should be implemented. Health-care providers should help older adults to find physical activities or exercise modalities that are perceived as pleasant. Caregivers of older adults with mental health issues should also be physically active, as this has a positive effect on the burden of carers of persons with mental health problems.