Little empirical evidence exists regarding developmental antecedents of borderline personality disorder (BPD) features in children and adolescents. As a first step in addressing this gap in our knowledge, this study examined the factor structure and stability of putative underlying BPD features, specifically impulsivity, negative affectivity, and interpersonal aggression, in 6-12-year-old girls. We report on results from exploratory and confirmatory factor analyses of underlying BPD dimensions as rated by parents and teachers over six successive data waves in a large, community sample of girls (N = 2,451). Six factors were derived from parent ratings (i.e., Cognitive Dyscontrol, (Lack of) Self-Control, Hostility, Depression/Anxiety, Hyperactivity, and Relational Aggression) and five factors were derived from teacher reports (i.e., Cognitive Dyscontrol, Hyperactivity, (Lack of) Self-Control, Relational Aggression, and Depression). The item composition of similar parent and teacher factors was highly consistent. The year-to-year stability from ages 6 to 12 was high for parent factor scores (r ranging from .71-.85) and moderately high for teacher factor scores (r ranging from .49-.77). These findings suggest that underlying dimensions of BPD features can be reliably measured and are stable in 6-12-year-old girls.