Based on a model of cognitive vulnerability to depressive relapse, mindfulness-based cognitive therapy (MBCT: Segal, Z.V., Williams, J. M. G., & Teasdale, J., Mindfulness-based cognitive therapy for depression. Guilford, 2002) was developed as a training program to provide patients with skills to become better at disengaging from maladaptive habitual patterns of thinking. Integrating mindfulness training with a cognitive framework, the program is now a firmly established option in the prevention and treatment of depression and has become a blueprint for mindfulness-based interventions addressing a wider range of emotional disorders. This chapter provides a brief overview of the theoretical model that guided the development of the program and the current state of the evidence from clinical trials and studies testing its mechanisms of action. While there is good evidence for the effectiveness of the program as a whole, open questions remain regarding the unique contributions and potential of mindfulness practice. Answering these will help to further advance the field and widen its application in the prevention and treatment of depression and associated conditions across the lifespan.