Understanding not only whether a therapy is effective but also how and why it works is essential for advancing evidence-based rehabilitation. Examining therapeutic factors provides insight into what makes treatment effective and lasting. This study investigated the mechanisms underlying a culturally adapted Cognitive-Behavioral Group Therapy (CBGT) for anger management in a Turkish juvenile correctional facility. Sixty male juvenile delinquents were randomly assigned to CBGT, a sharing (peer-support) group, or a waitlist control. Therapeutic processes were assessed using the Therapeutic Factors Inventory-Short Form (TFI-SF). Post-intervention interviews were analyzed using thematic analysis. A MANOVA revealed significant group differences on TFI-SF subscales, F(4,24) = 3.24, p = .02, ηp² = .35. Specifically, CBGT participants reported higher scores on Secure Emotional Expression and Social Learning than the sharing group. In both groups, emotional expression was the most salient factor. Thematic findings supported these results, highlighting group cohesion, emotional expression, and social learning as key processes that contribute to the overall experience. Context-specific elements—such as group rules, engaging activities, and the therapists' role—also enhanced participation and safety. Overall, findings suggest CBGT for anger management promotes skill development and supports relational and emotional growth critical for rehabilitation. Understanding how structured techniques interact with broader therapeutic factors provides valuable insight into the mechanisms of change for juvenile delinquents and helps inform group-based interventions.