Individuals with a borderline personality disorder (BPD) or BPD traits usually have a lifetime history of harmful behaviors. Emotion regulation difficulties are a risk factor for suicide, whereas adequate family functioning and well-being play an important protective role. This study aims to determine the role of emotion regulation difficulties, well-being, and family functioning in the suicide risk and non-suicidal self-injury (NSSI) in adolescents and young people with BPD traits. From a sample of 285 young people, 103 (36.1%) had BPD traits (mean age = 16.82, SD = 2.71), and 68.93% were females. The results showed significant differences in personal and family variables according to the type of harmful behavior. Suicide attempts (SA) were mainly predicted by difficulties in impulse control, whereas NSSI was predicted by low family satisfaction. Programs designed to prevent SA and NSSI should consider individual differences, as well as the type of harmful behaviors exhibited.