Objective: The aim of the present study was to compare the effectiveness of Mindfulness-Based Cognitive Therapy (MBCT) and Behavioral Activation (BA) therapy on irrational thoughts and depression in individuals with Generalized Anxiety Disorder (GAD). Methods and Materials: This applied research utilized a quasi-experimental method with a pre-test and post-test design. The statistical population included all individuals diagnosed with GAD who visited psychotherapy clinics in Mashhad in 2020. From this population, 45 participants were purposefully selected from the Nabz-e Zindagi Counseling Center in Mashhad and randomly assigned to three groups of 15 (two experimental groups and one control group). The subjects responded to the Irrational Beliefs Test (IBT) by Ahwaz and Mo'tamedi (2005) and the Beck Depression Inventory (BDI) (1961) at three stages: pre-test, post-test, and follow-up. The MBCT and BA therapies were administered to the experimental groups, while the control group did not receive any treatment. Data were analyzed using SPSS software. Findings: The results indicated that the main effect of the group on irrational thoughts and depression was significant in both experimental groups (p < .05). However, there was no significant difference in the impact of the two methods on irrational thoughts (p = .144) and depression (p = .950). Conclusion: Both treatments were equally effective in individuals with GAD. Therefore, both treatments can be utilized to reduce psychological problems in individuals with GAD.