Empirical evidence for the effectiveness of mindfulness-based cognitive therapy (MBCT) is encouraging. However, data concerning the role of mindfulness in its relapse preventive effect are lacking. In our study, 25 formerly depressed patients received MBCT. Mindfulness was assessed before and immediately after MBCT using the Mindful Attention and Awareness Scale. Mindfulness significantly increased during MBCT, and posttreatment levels of mindfulness predicted the risk of relapse/recurrence to major depressive disorder in the 12-month follow-up period. Mindfulness predicted the risk of relapse/recurrence after controlling for numbers of previous episodes and residual depressive symptoms. The results provide preliminary evidence for the notion that mindfulness is an important factor in relapse prevention in major depression.