This study piloted an 8-session Functional Analytic Psychotherapy group treatment for borderline personality disorder and compared its effects to an interpersonal skills training group. 49 clients diagnosed with BPD were randomly assigned to one of the two groups. Measures on intimacy, BPD symptom severity, and emotion regulation were taken before and after treatment, and at 6-month follow up. The FAP group showed statistically significant and large improvements over the interpersonal skills group on all measures, particularly intimacy. Regression analysis also found a reduction in the relationship between intimacy and BPD severity following FAP treatment. The results suggest FAP may be a useful adjunct treatment for improving social connection difficulties in BPD.