This article presents a conceptualization of personality disorders in adolescence and the adaptation of transference-focused psychotherapy (TFP) for personality disordered adolescents (TFP-A). The model of assessment and treatment presented is based on contemporary psychoanalytic object relations theory developed by Otto F. Kernberg and supported by findings from current evidence-based outcome research. We present a method of assessing personality disorders in adolescents that addresses the variability of personality disorder symptoms and traits among adolescents and their instability over time. We then present the goal of TFP-A and its major phases of implementation. A major focus is therapist interventions.