Unemployment is associated with a diminished mental health. Interventions to improve mental health for the unemployed exist. However, there is no clear overview with respect to the content and effectiveness of these interventions. A systematic search was conducted and, included studies that targeted unemployed adults, described an intervention and reported mental health as an outcome measure. After screening, 24 studies remained, which contained 21 different interventions. These interventions could be classified into three categories: occupational skills training interventions, psychological interventions and combined interventions. The majority of the studies reported significant short-term effects on mental health, but in most cases evidence of sustained effects was lacking or not assessed. There is promising evidence that interventions combining occupational skills and resilience training are effective in promoting mental health. However, there is a need for high-quality research on the intervention effects on the mental health of the (long-term) unemployed.