Epidemiological studies have suggested that childhood maltreatment increases suicidal ideation, and dissociative symptoms and hopelessness are involved in this relation. To better address this issue, we used a path analysis model to examine the role of different types of childhood maltreatment on suicidal ideation, investigating whether hopelessness and dissociative symptoms mediated this relation. A sample of 215 adult psychiatric inpatients was enrolled between January 2019 and January 2020, at the psychiatric unit of Sant’Andrea Medical Center in Rome, Italy. The Childhood Trauma Questionnaire (CTQ), Beck Hopelessness Scale (BHS), Dissociative Experiences Scale (DES-II), and Columbia-Suicide Severity Rating Scale (C-SSRS) were used to test the hypotheses. Results revealed that the presence of sexual abuse directly affected suicidal ideation (β = 0.18, SE = 0.8, p < 0.05), while emotional abuse and neglect indirectly increased suicidal ideation via dissociation (β = 0.05, SE = 0.02, 95% C.I. 0.01/0.09) and hopelessness (β = 0.10, SE = 0.03, 95% C.I. = 0.04/0.16). Professionals working with children should be aware of the long-term consequences of childhood maltreatment, particularly suicide risk. Furthermore, professionals working with adults should inquire about past childhood maltreatment.