The aim of the present study was to investigate the effectiveness of acceptance and commitment group therapy on self-disabling in obese adolescent girls. This study was applied in terms of purpose and quasi-experimental in terms of method with a pre-test-post-test design with a control group. The statistical population included all obese adolescent girls aged 13 to 16 years old in the first secondary schools of Tehran in the academic year 2024-2025. After initial mental health screening with the General Health Questionnaire (GHQ-28), 30 eligible individuals were selected by convenience sampling and randomly assigned to two experimental and control groups (15 people in each group). The experimental group participated in eight 90-minute sessions of acceptance and commitment group therapy, and the control group did not receive any intervention. The research instruments included the Jones and Rodewalt (1982) Self-Disabling Questionnaire. Data were analyzed using SPSS version 27. At the descriptive level, mean and standard deviation indices were calculated, and at the inferential level, univariate analysis of covariance and univariate follow-up tests were used. The results showed that the experimental group showed a significant decrease in self-handicapping compared to the control group (F = 24.81, p < 0.001, η² = 0.50). Accordingly, it can be concluded that acceptance and commitment group therapy is effective in reducing negative cognitive processes, including self-handicapping, in obese adolescents and can be used as an efficient intervention to improve the mental health of this group.