Borderline personality disorder (BPD) is characterized by instability in interpersonal relationships. To date no reviews have scoped the extant research on peer relationship functioning for young people diagnosed with BPD or showing borderline personality features. The current review provides this scoping of studies on all facets of peer relationships, including friendship quality, peer victimization and bullying and peer aggression, and relevant studies of social–cognitive processes with relevance to peer relationships. From 282 studies identified up to August 2019, 39 studies were included for review. The majority of these were published between 2014 and 2019 (64%), with most studies using community samples (56.4%), conducted in the Unites States of America (51.3%) and over half (53.8%) with majority female (> 60% of the sample) participants, and over half (53.8%) with adolescent samples (mean age between 13 and 18 years). Most studies only addressed one domain of peer relationships (general k = 15; friendships k = 12; victimization k = 10; aggression k = 12). Only 8 studies (19.5%) were identified that included measures that crossed these domains. Borderline personality features were consistently associated with problematic functioning across facets of peer functioning. However, relatively few studies were located that examined multiple domains of peer relationship qualities, leaving an unclear and disjointed body of research. Some promising directions have received scant attention, including unrealistic expectations of friendship exclusivity and the sequelae when those expectations are not met. Studies that explicitly probe the developmental role of dysregulation, that assess bully/victim co-occurrence, and that consider the dynamics of thwarted expectations for exclusive “best-friend” roles, especially within the context of potential disorganized attachment histories, are needed.