Introduction: depression is among those disorders that negatively influence cognitive, psychological and emotional process of the patients. Therefore, the present study was conducted aiming to investigate the effectiveness of group reality therapy on the negative automatic thoughts and psychological flexibility of depressed clients at consultation centers. Materials and Methods: the present study was quasi-experimental with pretest, posttest, control group design and two-month follow-up stage. The statistical population of the present study included clients with depression who referred to consultation centers in the autumn and winter of 2019-2020 in the city of Ahvaz. 40 people with depression were selected from the statistical population through purposive sampling method and they were randomly accommodated into experimental and control group (each group of 20). The experimental group received ten ninety-minute sessions of reality therapy (Glasser, 2013) during two and half months. The applied questionnaires in this study included depression questionnaire (Beck et. al, 1996), negative automatic thoughts questionnaire (Kendal and Holon, 1980) and psychological flexibility questionnaire (Denis and Wanderwal, 2010). The data from the study were analyzed through repeated measurement ANOVA. Results: the results showed that group reality therapy has significant effect on the negative automatic thoughts and psychological flexibility of the depressed clients at consultation centers (p<0. 001) in a way that this therapy succeeded in improving the decrease of negative automatic thoughts and improving psychological flexibility of depressed client at consultation centers. Conclusion: the findings of the present study revealed that reality therapy can be applied as an efficient therapy to decrease negative automatic thoughts and improve psychological flexibility of the people with depression through employing techniques such as the members’,familiarity with their responsibilities and helping acceptance and increasing accountability and also underplaying the past in the present behavior and emphasizing internal control.