Witnessing violence against a parent as a child entails a heightened risk of the child developing problems such as post-traumatic stress, depression, behavioral problems, or difficulties with social relationships. Knowledge about the effectiveness of methods developed to support children who have witnessed violence against their mothers is needed. This presentation reports the results from a national evaluation with the aim to study changes in the health and wellbeing of children after participating in support interventions. Eight group-based or individual support interventions directed at children who had witnessed violence against their mother from her partner were compared to: child and adolescent psychiatry, women’s shelters, and the social services, including the individual and family services, and family law. This report is based on mothers’ ratings of 295 children between 3 and 13 years of age, and self-ratings from 64 of these children, aged 9 to 13 years. The study is based on measurements at three times; before or in connection with the start of the intervention (pre-test), when the child had finished the intervention 4 to 6 months later (post-test), and one year after the child started the intervention (one-year follow-up). The mothers, and any 9 to 13-year-old children who agreed to participate, were interviewed and filled out questionnaires about psychological health and wellbeing. Measures included the Strengths and Difficulties Questionnaire, the Trauma Symptom Checklist for Children (TSCC), and measures of emotion regulation and general psychological well-being. The agencies offering support aimed directly at children tended to have better effect than agencies not providing support aimed at children. Generally, children with a high degree of psychological illness at pre-test improved more than children with fewer difficulties. However, the effect sizes were small, and at the one-year follow-up the mothers still rated their children’s psychological illness considerably higher compared to “children in general”. Further, children whose mothers had been subjected to physical violence during the last six months tended to have a more negative development in psychological health, younger children’s psychological health tended to improve more compared to older children’s, and longer interventions had better effect than shorter ones. The implications of these results for practice are discussed.