Interpersonal difficulties are a widely accepted characteristic of borderline personality disorder (BPD). However, the results of empirical findings of deficits in social-cognitive abilities that may underlie interpersonal difficulties in this population have been mixed. In this paper, we review the literature on social-cognitive impairment in BPD by organizing studies based on patterns of positive and negative of findings. We provide a new model of mentalizing impairment in BPD by integrating findings into one framework that suggests hypermentalizing as the core feature of social-cognitive impairment in BPD. We review data in support of a hypermentalizing model of BPD and situate this data in the broader context of current work on hypermentalizing.