The multiple‐family group intervention is an effective, yet affordable, 8‐week treatment that is conducted in a juvenile correctional institution in Alabama with adolescents who sexually offend and their families. Data from 115 incarcerated male adolescents and their male and female caregivers collected at pre‐, post‐, and 1‐year follow‐up were used to determine that problem behaviors (internalizing, externalizing) decreased over pre‐ and posttest and the significant decreases in maladaptive emotion regulation predicted those changes. Adolescent‐reported anxiety over abandonment and attachment dependence on parents increased significantly; these changes were predicted by decreases in maladaptive emotion regulation. Linear growth models were also fit over the 3 time points and indicate decreases in adolescent problem behavior and maladaptive emotion regulation.