Background: Identifying specific mechanisms of risk can help better tailor parenting interventions to different forms of maternal psychopathology. Borderline personality disorder (BPD) symptoms interfere with mentalization and emotion regulation capacities; thus, maternal BPD symptoms may uniquely impact aspects of parenting that draw on these capacities. Objective: This study examines whether BPD symptoms are independently associated with specific parent-child relatedness factors beyond maternal depressive symptoms, and whether these factors predict subsequent child maladjustment in the context of BPD symptoms. Method: At two points over one year, a United States community sample of 214 mothers of children aged 3-18 completed self-report measures on parenting and mental health, open-ended questions about parenting experiences, and computerized mentalization tasks. Analyses included partial correlations and regression approaches to mediation and moderation. Results: Controlling for depression, mothers with more BPD symptoms reacted with greater hostility towards their child, put more blame on their child for misbehavior, and felt more dissatisfaction in the relationship. Maternal BPD symptoms did not directly predict increased child maladjustment but did interact with several parenting measures to predict subsequent child maladjustment. For mothers high in BPD symptoms, negative emotionality associated with parenting and beliefs about children's negative emotions predicted increased child internalizing and externalizing symptoms at follow-up; these same interactions did not emerge for depressive symptoms. Conclusions: Results suggest BPD symptoms may be linked to specific types of parenting risks relative to maternal depressive symptoms, and that the meaning of certain parenting risk factors differs depending on BPD symptoms levels.