Borderline personality disorder (BPD) represents a severe distortion in the development of attachment, self, and emotion regulation. Study of children at high risk of developing BPD may inform precursors to BPD. In a low socioeconomic status sample of 30 children aged 4–7 whose mothers have BPD and 30 normative comparisons, representations of the caregiver–child relationship and of the self, and emotion regulation were assessed with a story-stem completion measure. In contrast to comparisons and controlling for major depressive disorder, children whose mothers have BPD told stories with the following: (a) more parent–child role reversal, more fear of abandonment, and more negative mother–child and father–child relationship expectations; (b) more incongruent and shameful representations of the self; and (c) poorer emotion regulation indicated by more confusion of boundaries between fantasy and reality and between self and fantasy, more fantasy proneness, less narrative coherence, and marginally more intrusion of traumatic themes. In the sample as a whole, (a) a maladaptive caregiver–child relationship composite was associated with maternal identity disturbance and self-harm; (b) a maladaptive self-composite was associated with maternal self-harm; and (c) a maladaptive emotion regulation composite was associated with maternal identity disturbance, negative relationships, and self-harm. Results are discussed in terms of putative precursors to BPD and preventive interventions.