Warfare severely impacts children’s mental health, making them susceptible to Secondary Traumatic Stress (STS). This study examines the effectiveness of an expressive art therapy intervention based on the Coping Cat Program to address these issues. Employing a mixed-methods approach, the study progresses through three phases: a qualitative assessment of war-affected children’s mental health, the development of a culturally relevant art therapy intervention reviewed by experts, and the validation of the intervention using the Lawshe model and Content Validity Index (CVI), achieving a high efficacy score (0.89). A randomized controlled trial (RCT) with twenty children exhibiting STS symptoms was conducted, with ten children receiving the art therapy intervention. Statistical analysis showed significant reductions in STS symptoms for the intervention group, sustained over a 3-month follow-up. This study highlights the potential of the Art-Therapy Intervention based on the Coping Cat Program to enhance the mental health of war-affected children, recommending broader implementation and further research.