Introduction: A juvenile detention center is a place where teenagers with risky behaviors, such as competitiveness, separation from family, impatience, aggression, physical abuse, suicide, addiction, and theft, are kept to be corrected and trained. Acceptance and commitment therapy (ACT) can greatly reduce high-risk behaviors in these individuals. Objective: This study aimed to investigate the effect of ACT on the risk-taking behaviors of delinquents in a juvenile detention center. Materials and Methods: This quasi-experimental study was performed on 60 male juvenile delinquents aged 12-18 years in a juvenile detention center in Southeast Iran. The participants were recruited by the census method and assigned to the intervention and control groups (30 in each group) using simple random sampling. The participants in the intervention group attended eight 90-min sessions of ACT, and the participants in the control group received routine training in the center. Iranian adolescents’ risk-taking scale was used to assess the risk-taking of samples before and one month after the ACT intervention. The study data were analyzed using descriptive (frequency, percentage, mean, and standard deviation) and inferential statistics (independent samples t-test, paired-samples t-test, chi-square test, and the analysis of covariance). Results: Most adolescents in the intervention and control groups were in the age group of 16-20 years (96.7%, and 93.3%, respectively) and had a middle school degree (56.7%, and 40%, respectively). A comparison of the mean risk-taking behaviors scores in the intervention (56.53±11.4) and the control groups (57.28±11.18) showed that the participants in both groups were engaged in high-risk behaviors and were similar. However, in the post-test stage, the mean risk-taking behaviors score in the intervention group decreased (39.64±10.26) compared with the control group (56.31±11.5) with a significant intergroup difference (P<0.05). Also, the Mean±SD risk-taking scores after the intervention were higher than the control group calculated by the covariance analysis for the intervention group participants. These differences were statistically significant (Cohen’s d=15.24, 95% CI, 10.91%-19.56%). Conclusion: According to the results, ACT reduced high-risk behaviors in juvenile delinquents. Thus, such psychological interventions can be performed to reduce high-risk behaviors in vulnerable groups such as adolescents in juvenile detention centers. Also, the effectiveness of these interventions can be evaluated in longitudinal studies.