Borderline personality disorder is a significantly disabling disturbance often arising in adolescents or young adults. In the absence of demonstrated effective treatments in this population, this open prospective study evaluated the effect of low dose (3 mg per day) flupenthixol in 13 rigorously diagnosed adolescents with borderline personality disorder. Therapeutic outcome over eight weeks of treatment assessed across measures of impulsivity, depression/dysphoria, general psychopathology and global functioning showed significant improvement in all spheres. These findings suggest that low dose flupenthixol may have a role to play in the short-term treatment of this population.