Borderline personality disorder (BPD) is a disorder characterized by severe disturbances in emotion regulation. In Dialectical Behavior Therapy (DBT), affect dysregulation is seen as a consequence of a transaction between a biological predisposition to emotion vulnerability and invalidating environmental experiences. In the past few years, a growing body of research has accumulated demonstrating the efficacy of DBT in treating severely disordered, chronically suicidal, and substance-dependent individuals with BPD. This article describes a DBT approach to the treatment of emotion regulation in individuals with BPD.