Complex post-traumatic stress disorder (cPTSD) is a clinical condition that features not only PTSD symptoms, but also disturbances in self-organization. Patients with cPTSD have a higher incidence of psychiatric comorbidities, including suicidality. A key construct tightly related to suicidality is hopelessness, described as a feeling of despair, with a state of mind giving low or negative expectancies regarding one's future. Since there is a paucity of studies investigating the link between cPTSD and hopelessness as a risk factor for suicidality, the aim of this study was to examine the role of post-traumatic symptomatology as the primary driver of suicidality, as measured by hopelessness. 211 patients were enrolled and divided into two groups: PTSD (143 patients) and cPTSD (78 patients). A set of standardized measures was administered to study post-traumatic symptomatology, depression, and hopelessness. The results showed that compared to PTSD, cPTSD patients experienced more severe symptoms in all clinical outcomes (p < 0.001). The mediation analysis revealed a significant positive association between post-traumatic symptomatology and hopelessness in the cPTSD group, which was not significant in the PTSD group. Among PTSD patients, depression mediated 43.37% of the impact of post-traumatic symptomatology on suicidal ideation. Our results contribute to a better understanding of complex post-traumatic symptomatology, further highlighting its role in the pathogenesis of suicidality. Hence, these findings have important clinical implications, suggesting that targeted, trauma-focused interventions might effectively prevent hopelessness and therefore suicide risk in patients with cPTSD.