The aim of this review was to assess the effectiveness of psychosocial interventions for the promotion of mental health and prevention of depression among older people. A systematic review of prospective controlled trials was conducted including 69 studies. The studies were divided into physical exercise, skill training, reminiscence, social activities, group support and multicomponent interventions. Data from 44 trials contributed to a meta-analysis of effectiveness. Overall, psychosocial interventions had a positive effect on quality of life and positive mental health. The pooled interventions also had a statistically significant effect on reduction in depressive symptoms. Social activities significantly improved positive mental health, life satisfaction and quality of life and reduced depressive symptoms. Based on the results of this study, duration of interventions is of importance, since interventions lasting for >3 months exhibited more positive effects compared with shorter interventions. Meaningful social activities, tailored to the older individual's abilities and preferences should be considered in aiming to improve mental health among older people.