The diagnosis of borderline personality disorder (BPD) in adolescents has been controversial. Thus, few studies have examined BPD in suicidal adolescents, even though it is strongly associated with suicidal behaviours in adults. This study examines differences between suicidal adolescents with (n = 47) and without (n = 72) BPD on history and characteristics of suicidal behaviour, Axis I co-morbidity, affect regulation and aggression. Assessments were completed with both adolescents and parents, and consensus ratings based on best available data were analysed. BPD participants were more likely to have a history of suicide attempts and to have been admitted because of a suicide attempt (vs. suicidal ideation). There were no significant differences in self-injurious behaviours or degree of suicidal ideation. BPD participants also had more psychiatric co-morbidity and higher aggression scores but no significant differences in affective dysregulation compared with suicidal adolescents without BPD. Diagnostic stability over 6 months was modest. Our results demonstrate that, compared with other acutely suicidal adolescents, the clinical profile of BPD participants is unique and suggests an increased risk for suicidal behaviours. This extends upon other studies that support the construct validity of BPD during adolescence and suggests that BPD should be considered in suicide risk assessment for adolescents. Copyright © 2012 John Wiley & Sons, Ltd.