<p>This study aimed to examine the effects of a psychoeducation program based on mindfulness-based cognitive therapy on mindfulness, cognitive defusion, and depression levels in patients with depression. A randomized controlled design was employed. Eighty patients diagnosed with depression who applied to the psychiatry outpatient clinics of a state hospital and met the inclusion criteria were randomly assigned to two groups. The intervention group received a psychoeducation program based on mindfulness-based cognitive therapy once a week for eight weeks, with each session lasting 60&#xa0;min. No intervention was provided to the control group. Data were collected in three phases (pre-test, post-test and follow-up) using the Mindfulness Attention Awareness Scale, Cognitive Defusion Scale, and Beck Depression Inventory. Data were analyzed for 66 participants. Following the intervention, mindfulness (F = 85.472, ηp² = 0.572, <i>p</i> &lt; 0.001) and cognitive defusion (F = 54.987, ηp² = 0.462, <i>p</i> &lt; 0.001) levels in the experimental group increased significantly, while depression levels decreased significantly (F = 41.538, ηp² = 0.394, <i>p</i> &lt; 0.001). These effects were sustained at the three-month follow-up assessment. The results demonstrate that mindfulness-based psychoeducation was effective in improving mindfulness and cognitive defusion and decreasing depression levels among patients with depression. These findings suggest that integrating mindfulness-based approaches into clinical practice may enhance the effectiveness of depression treatment.</p>