According to available studies concerning treatment of patients with borderline personality disorder, mood stabilizers have been found effective in controlling core symptoms of borderline pathology, in particular impulsive behavior and mood instability. Oxcarbazepine, an anticonvulsant structurally related to carbamazepine, has been tested in psychiatric settings for treating patients with bipolar disorders, substance abuse, resistant psychosis, and schizoaffective disorder. The present article is a pilot study on the efficacy and tolerability of oxcarbazepine in the treatment of borderline personality disorder. Seventeen outpatients diagnosed with DSM-IV-TR borderline personality disorder were included. Patients were administered oxcarbazepine, 1200 to 1500 mg/day supplied twice daily, and tested at baseline, week 4, and week 12 using the Clinical Global Impressions scale-Severity of Illness item (CGI-S), the Brief Psychiatric Rating Scale (BPRS), the Hamilton Rating Scales for Depression and Anxiety (HAM-D, HAM-A), the Social Occupational Functioning Assessment Scale, and the Borderline Personality Disorder Severity Index (BPDSI). Adverse effects were collected and serum sodium level was measured. Statistics were performed by using the analysis of variance for repeated measures. Four patients discontinued treatment in the first 4 weeks due to noncompliance. A statistically significant response to oxcarbazepine was observed according to CGI-S and BPRS mean score (p = .001), HAM-A mean score (p = .002), BPDSI total score (p = .0005), and 4 BPDSI items, including interpersonal relationships (p = .0005), impulsivity (p = .0005), affective instability (p = .0005), and outbursts of anger (p = .045). No cases of significant hyponatremia or severe adverse effects were reported. Mild to moderate adverse effects included sedation, dizziness, nausea, and headache. Seven patients reported no adverse effects. Oxcarbazepine was found an effective and well-tolerated treatment in the management of borderline personality disorder patients.