Interpersonal dysfunction is central to borderline personality disorder (BPD). Recent research has focused on the role of oxytocin (OT) in BPD, with mixed results regarding the processing of social information. Fifteen BPD patients and 15 controls participated in two clinical interviews, one under OT and one under placebo, which were randomly conducted 1 week apart in a double-blind fashion. Nonverbal behavior was evaluated using the Ethological Coding System for Interviews. Childhood trauma was examined using the Childhood Trauma Questionnaire. The patients with BPD showed less affiliative behavior than the controls. Notably, the controls, but not the patients, displayed more affiliation when OT was given at T1 compared with OT given at T2. OT was also associated with less flight behavior in both groups when given at T1 compared with placebo. OT responses were unrelated to the patients' history of childhood trauma. The present findings are informative with respect to patients' nonverbal prosocial behavior in clinical settings.