Suicide is a leading cause of death worldwide. Identifying biomarkers will help enhance our understanding of suicidal pathophysiology and improve its prevention. Therefore, we investigated CRP levels in 600 depressed inpatients: 520 patients had a lifetime history of suicide attempts and 80 patients did not have any history of suicide attempts. For all patients, we assessed socio-demographic features, lifetime Axis I DSM-IV diagnoses, depression intensity, suicidal ideation, characteristics of suicidal history, and history of childhood trauma. The day following admission, fasting blood tests yielded samples collected for the measurement of high sensitivity hs-CRP. CRP levels were associated with a history of suicide attempts. The risk of suicide attempts increased with higher levels of CRP in a dose-response way before and after adjustments for age, gender, chronic diseases, addiction and anxiety comorbidities, antidepressants use, smoking status and sexual abuse. Noteworthy, the association between CRP levels and history of suicide attempts remained significant after having excluded patients with chronic diseases. There was no significant difference in CRP levels between patients who attempted suicide more or less than a week before plasma sampling, and no significant difference in CRP levels was evidenced between high vs low suicidal ideation. In conclusion, this is the first study suggesting that CRP may be a trait marker for suicidal vulnerability by associating CRP levels and a lifetime history of suicide attempts in depressed inpatients. Therefore, determining the inflammatory marker profile of individuals exhibiting suicidal behaviors could be relevant for anticipating behaviors and refining new therapeutic opportunities.