Research on mental health issues, such as anxiety and depression, which have become prevalent among pre-adolescents and lead to impaired functioning in family, academic, and social domains, is critically important. One prominent theoretical approach to explaining anxiety and depression symptoms is Acceptance and Commitment Therapy (ACT) and its Psychological Inflexibility Model. This study aims to elucidate the relationship between psychological inflexibility levels in pre-adolescents and their anxiety and depression levels. The Revised Children's Anxiety and Depression Scale--Child Version (RCADS) and the Avoidance and Fusion Questionnaire for Youth (AFQ-Y8) Child Form were used as data collection tools. Data were collected from 327 sixth-grade students (178 male and 149 female) attending three different public schools in Gaziantep, and a simple linear regression model was established with the obtained data. The findings indicated that psychological inflexibility significantly predicts internalizing disorder levels (R = 0.716, R Square = 0.513; p <0.01), total anxiety levels (R = 0.668, R Square = 0.446; p <0.01) and depression levels (R = 0.692, R Square = 0.479; p <0.01) of pre-adolescents. These results contribute to the literature on explaining anxiety and depression in pre-adolescents, and future studies should investigate the relationship between psychological inflexibility and externalizing problems such as aggression and anger.