Attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent psychiatric disorder in adolescence and results severe impairment. Few psychosocial interventions aim at ADHD in adolescence and are rarely evaluated in randomized controlled trials (RCTs). Therefore, an intervention combining adolescent-directed problem-solving and organizational skills training with behavioral parent and teacher training has been developed. Its efficacy in comparison to waiting list and active controls is reported. One hundred thirteen adolescents (mean age 13.99 years) with ADHD were randomly assigned to the training, a waiting list or an active control condition (progressive muscle relaxation [PMR]). Parents and teachers rated ADHD symptoms, academic enablers, and comorbid problems before and after. Results: The training significantly reduced ADHS symptoms and parent- and teacher-rated internalizing problems and increased teacher rated academic enablers compared to waiting list controls. Compared to active controls, results were in the range of small nonsignificant effects. A skills training is an efficacious treatment for adolescent ADHD, however, not significantly superior to PMR. Contrasts between both interventions need to be further investigated.