Millions of children and adolescents who have survived armed conflict and displacement face increased risks of post-traumatic stress reactions, depression, anxiety and behavioral problems. Decades of research show that evidence-based mental health interventions and psychosocial support (MHPSS) can reduce mental distress even in active fragile and conflict-affected settings. Despite growing evidence of effectiveness, such interventions are often limited to pilot research with short-term funding and are rarely translated into sustainable, high-quality MHPSS systems. War and displaced settings, such as camps for internally displaced people or refugee camps and informal settlements, have national health and social care systems that cannot meet the growing demand for mental health. An example is a common elements treatment approach over the phone among Syrian refugee children in Lebanon, which showed promising reductions in symptoms of anxiety, depression, and trauma, but only reached a fraction of those needed. The article highlights the need to expand the reach and strengthen MHPSS systems in these settings.