To compare clinical traits of suicidal vulnerability among in-patients with suicidal behavior disorder (SBD) with and without borderline personality disorder (BPD). Method: we recruited adult patients with SBD, consecutively and voluntarily hospitalized in a specialized unit for affective disorders and suicidal behavior between July and October 2016. Ninety-two inpatients having attempted suicide within the past 2 years were divided into two subgroups according to the presence or absence of BPD. Clinical vulnerability traits for suicidal behavior were assessed. Results: Half of the patients with SBD also had BPD. Patients with BPD were nine times more likely to be major suicide repeaters compared to those without. They were also more likely to display clinical and psychological vulnerability traits for suicidal behavior, even after considering potential confounders. Emotional dysregulation, shame-proneness, impulsiveness, preoccupied attachment pattern, and childhood trauma were high in both groups, but significantly increased in those with (vs. without) BPD status. Psychological traits remained stable in SBD-BPD patients, regardless of the time since the last suicide attempt (i.e. SBD in recent vs. early remission). Conclusions: Clinical and psychological traits associated with suicidal vulnerability are present in all SBD patients compared to non-suicidal populations, but comorbidity with BPD is associated with particularly high scores. BPD could be considered as a specifier for SBD diagnoses.