This chapter offers an overview of the history and development of Dialectical Behaviour Therapy (DBT) and the treatment's theoretical underpinnings. In the context of establishing an effective treatment for clients suffering with severe and enduring psychological difficulties, the discussion considers the process whereby Marsha Linehan incorporated dialectical and acceptance philosophies within a traditional behavioural approach to treatment. This process demonstrates the synthesis between the technology of change and the practice of acceptance using the principles of dialectics. The relevance of the key therapeutic strategies which form the foundations of the therapeutic interventions are explored; these include behavioural science, acceptance, mindfulness, dialectics, and the biosocial theory.