Background and Aim: Internet addiction, high-risk behaviors, and bullying are prevalent challenges during adolescence, often rooted in family dynamics. This study aimed to investigate the effectiveness of a family-based intervention, Acceptance and Commitment Therapy (ACT)-based parent-child relationship training, on these three problem variables in students.

Methodology: In a quasi-experimental pre-test/post-test control group design, 80 parent-child dyads were randomly assigned to an experimental group and a control group. Parents in the experimental group participated in an 8-session ACT-based training program. Students in both groups completed the Young's Internet Addiction Test, the Iranian Adolescent Risk-taking Scale, and the Illinois Bullying Scale at both stages. Data were analyzed using multivariate analysis of covariance (MANCOVA).

Findings: The multivariate tests revealed a significant overall effect for the intervention . Subsequent univariate analyses indicated that, after controlling for pre-test scores, the experimental group students showed significantly lower scores in internet addiction , high-risk behaviors , and bullying compared to the control group.

Conclusion: Parent training based on Acceptance and Commitment Therapy principles is an effective strategy for concurrently reducing a wide range of externalizing problem behaviors in adolescents. This finding underscores the importance of family-based interventions that focus on enhancing parental psychological flexibility.