In this article, the process of mentalizing, its components, and role in self-regulation and attachment are reviewed. An examination is presented of the neurodevelopmental changes affecting the adolescent’s capacity to mentalize and the role of such compromised mentalizing in the adolescent’s vulnerability to adaptive breakdown and psychopathology, in general, and to emerging personality disorders, in particular. The principles, objectives, and core features of mentalizing-based treatment and its application to adolescents and families are discussed.