Background: The non-pharmacological interventions for behavioral problems of adolescents diagnosed with attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) are of great interest to researchers. Objectives: This study aimed to examine the efficacy of group reality therapy in behavioral symptoms in ADHD and ODD. Methods: Forty patients diagnosed with ADHD and ODD between 12 and 18 years were randomly assigned to two groups. The patients in the intervention group were participated in group reality therapy for five 120-minute sessions, once a week. The patients in the control group were enrolled in five unstructured sessions without intervention. Conners Parent Short Form questionnaire, Strengths and Difficulties Questionnaire (SDQ), and depression, anxiety, and stress scale (DASS-21) were performed at baseline, the sixth week, and the tenth week for follow-up. Results: Conners test showed a statistically significant difference in the intervention group in hyperactivity (P = 0.005), conduct (P < 0.001), and total score (P < 0.001) in the sixth week, as well as in conduct (P = 0.001), and total score (P = 0.008) in the tenth week. SDQ test analyzed based on partial Eta squared test, indicated the effect size in the intervention group was 81% and in the control group was 27%. Moreover, the DASS test in the intervention group showed improvement in depression, anxiety, and stress scores (P < 0.001). Conclusions: Group reality therapy is effective in the improvement of disruptive behaviors and emotional symptoms in ADHD and ODD.