Many people experience harm from someone else’s addiction. These people are called “affected others”. Some interventions target affected others directly. This article reviewed studies of the effectiveness of interventions targeted at affected others. The authors found 22 relevant articles. About 70% of these studies focused on interventions for alcohol-related harms, while 20% focused on gambling harms and 10% focused on illicit drugs. Many of these studies had medium some concerns to or high risk of bias. Overall, the results showed that affected other interventions appeared to increase life satisfaction and coping skills and decrease depressive symptoms for affected others. They also appeared to decrease relationship discord and help get the people with the addiction to start treatment. These outcomes were measured right after the intervention finished. No intervention effects were observed at short-term follow-up. More research is needed to understand longer-term outcomes.