Childhood trauma is intimately related with suicidal behaviour. Patients who have suffered childhood trauma develop impaired Reflective Functioning (RF), which refers to the capacity to understand ourselves and others in terms of intentional mental states. An improvement in RF has been associated with a reduction in suicidal attempts, but the mediating role of RF between childhood trauma and suicidal behaviour has not been addressed so far.We aim to examine the potential mediating effect of RF among childhood trauma and suicide attempts.We included 748 patients who had attempted suicide at least once. They were asked to complete the Reflective Functioning Questionnaire (RFQ-8), the Columbia-Suicide Severity Rating scale (CSSRS), and the Childhood Trauma Questionnaire-Short Form (CTQ-SF). We conducted linear regressions by simple mediating model to examine the role of RF in the indirect association between childhood trauma and the number of suicide attempts.Our results show significant indirect effects through hypo and hypermentalizing between Emotional Abuse (EA) and Sexual Abuse (SA) in childhood and the number of suicide attempts in lifetime. These results indicate that ineffective RF significantly mediates the association between childhood trauma and suicidality.This is the first study supporting the mediational role of RF in the relationship between EA and SA, and the number of suicide attempt in lifetime. These findings have important implications for reducing suicide rates and preventing future re-attempts. Further studies analysing this mediating role and focusing efforts on increasing RF-based interventions are required.