The present study aimed to investigate the effectiveness of group reality therapy on depression and self-esteem of high school students with depression. This study was designed as a quasi-experimental study with a pre-test and post-test design with a control group. The statistical population included all high school students in Ardabil city who had symptoms of depression. Of these, 34 people were selected using a multi-stage sampling method and randomly divided into two experimental and control groups, 17 people in each group. The experimental group underwent group reality therapy training in 12 60-minute sessions, while the control group did not receive any intervention. To measure depression and self-esteem, the Beck Depression Inventory, Second Edition (BDI-II) and the Rosenberg Self-Esteem Scale were used. Pre-test and post-test data were analyzed using multivariate analysis of covariance (MANCOVA). The findings showed that after the intervention, the mean depression scores in the experimental group decreased significantly and the mean self-esteem scores increased significantly, compared to the control group (p < 0.001). These results indicate that group reality therapy can be used as an effective psychological method to reduce depression and enhance self-esteem in high school students. Also, the findings show that group education and active participation of students in meetings play an important role in increasing self-awareness, problem-solving skills, and the ability to face psychological and social problems. Therefore, the use of group reality therapy in schools can be useful as a preventive and therapeutic strategy to improve the mental health of adolescents and help improve their quality of life and academic performance.