Objective: This study aimed to develop and validate a comprehensive self-report questionnaire to assess emotional and behavioral problems and psychological trauma in maltreated children. Methods: The Mental Health Scale for Maltreated Children (MHS-MC) was constructed to encompass five major symptoms (depression, anxiety, inattention/hyperactivity/impulsivity, aggression/defiance, and psychological trauma) prevalent in maltreated children. Critical items and ego-resilience subscale were also devised to increase clinical utility. After informed consent, 205 children (maltreated children, n=157, 76.6%) were recruited nationwide, and they answered a package of self-report measures, including the MHS-MC. Reliability, construct validity, concurrent validity, and criterion-related validity were examined to explore the psychometric properties. Results: The reliability was good to excellent. Confirmatory factor analysis yielded a five-factorial solution for the symptom subscales supporting construct validity. In logistic regression, the total scores of the MHS-MC predicted membership in the maltreated group. Criterion-related validity was generally satisfactory in that all subscales of the MHS-MC showed significant correlations with relevant measures in the expected direction. Conclusion This is the first attempt to develop a comprehensive psychological scale based on nationwide data collected from maltreated Korean children. We hope that the continued standardization of this scale will contribute to evidence-based clinical and policy decisionmaking for maltreated children.