Dialectical Behaviour Therapy (DBT) is a principle-based treatment synthesising two contrasting theoretical approaches, behaviourism, and mindfulness, under the philosophical umbrella of dialectics. Therapists seeking to develop competence in the treatment must acquire not just the knowledge and competencies aligned with each of these theoretical bases of the treatment but also a complex set of ‘if–then’ rules about when to apply any given principle. The treatment itself and the knowledge base for the curriculum is contained in two manuals: Linehan’s 1993 manual Cognitive-behavioral treatment for borderline personality disorder and the 2015 second edition of her DBT skills training manual. The chapter begins by reviewing the core elements of these manuals describing the curricula necessary to build the foundation of competence in the treatment. Like any psychological treatment, therapist competence develops following supervised practice where the knowledge within the curricula can be applied across a range of different contexts enhancing understanding and skill development. This chapter will describe a typical journey in acquiring skill in DBT, will address the issues to consider for those with the responsibility for training others in the treatment, describe the national and international context for certification and accreditation, and close with a consideration of cultural issues as they pertain to the treatment and training in the treatment.