Objective: To provide a systematic review of measures of interpersonal functioning used in treatments for people diagnosed with borderline personality disorder (BPD) and to report the effectiveness of treatments on these measures of interpersonal functioning. Method: Literature was reviewed using the online databases and reference lists of previous systematic reviews. Selected studies were randomized controlled trials (RCTs) that examined psychotherapeutic interventions for people with BPD and contained quantitative outcomes on various aspects of interpersonal functioning and reported their results in peer-reviewed journals. Reliability and validity of the results were evaluated. Results: Nineteen RCTs met our inclusion criteria. We found 16 different (sub)scales that measured some aspect of interpersonal functioning. Only four instruments were used by more than one research team. There is some evidence that psychotherapeutic interventions have beneficial effects on some aspects of interpersonal functioning in people diagnosed with BPD, both after individual and group therapy. Generalizability of these findings is limited. Conclusion: There is preliminary evidence that psychotherapeutic interventions have beneficial effects on various aspects of interpersonal reactivity that characterize people diagnosed with BPD. However, none of these effects have a robust evidence base. There are serious concerns about the lack of agreed-upon concepts and instruments.