Dialectical Behaviour Therapy can be conceptualized as the transaction between behaviour therapy and Zen contemplative practice, held together with a dialectical philosophy. When first developed, mindfulness practices had not yet been incorporated into psychotherapy. Marsha Linehan chose to augment behaviour therapy with Zen practice. This chapter begins with a brief history of Zen and discusses the need for an acceptance-based practice to balance behaviour therapy within the treatment. It describes the Zen beliefs contained in the four noble truths and precepts, and how these translate into the principles and practice of Zen. It then considers both the differences between and compatibility of Zen and behaviour therapy. Finally, it discusses how Zen practice modifies behaviour therapy in DBT. Most of the stories and anecdotes are from Linehan’s Zen Dharma talks given during her Zen Sessions held over the past ten years.