This study was conducted to validate and adapt the Behavior Assessment System for Children, Third Edition (BASC-3), for adolescents aged 12 to 14 in Tehran. The research followed a descriptive-correlational design based on structural equation modeling (SEM). The research population was comprised of all adolescents aged 12 to 14 enrolled in lower secondary schools in Tehran. Using stratified random sampling across five regions of Tehran (Northwest, Northeast, Southwest, Southeast, and Center), 450 participants were selected from four schools per region. The instruments used were the Parent Rating Scale (PRS) and Teacher Rating Scale (TRS) of the BASC-3, which possess established validity and reliability in their original versions. SEM results indicated that the Cronbach’s alpha for the Parent Form was 0.91 and for the Teacher Form was 0.93, demonstrating excellent internal consistency. Based on the factor analysis, all items loaded onto a single factor. Consequently, these questionnaires are recommended for use in clinical and educational assessments.