The antecedents and developmental course of borderline personality disorder symptoms were examined prospectively from infancy to adulthood using longitudinal data from a risk sample (N = 162). Borderline personality disorder symptom counts were derived from the Structured Clinical Interview for DSM Disorders diagnostic interview at age 28 years. Correlational analyses confirmed expected relations between borderline symptoms and contemporary adult disturbance (e.g., self-injurious behavior, dissociative symptoms, drug use, relational violence) as well as maltreatment history. Antecedent correlational and regression analyses revealed significant links between borderline symptoms in adulthood and endogenous (i.e., temperament) and environmental (e.g., attachment disorganization, parental hostility) history in early childhood and disturbance across domains of child functioning (e.g., attention, emotion, behavior, relationship, self-representation) in middle childhood/early adolescence. Process analyses revealed a significant mediating effect of self-representation on the relation between attachment disorganization on borderline symptoms. The findings are discussed within a developmental psychopathology framework in which disturbance in self-processes is constructed through successive transactions between the individual and environment.