Emergency departments (EDs) play an increasingly crucial role in the management of patients with suicidal behavior (SB). Demoralization has been associated with SB in various populations and conditions, but little is known about the effect of this construct in SB patients who attend an ED. Therefore, a more inclusive SB assessment which considers the demoralization construct could be useful in clinical practice. The main aim of this study was to assess the presence and severity of demoralization in patients visiting EDs for SB. Secondly, the maintenance of the relationship between demoralization and SB after controlling for depression and the proportion of variance which accounted for hopelessness was investigated. A cross-sectional study of patients (N = 199) visiting an ED for SB was performed, which examined the role of demoralization, hopelessness, and depression on suicidal ideation (SI) and suicide attempts (SAs). Demoralization was strongly and positively correlated with SI. Demoralization was related to major depressive episodes, but it was confirmed to be a different and, probably, more sensitive construct for SB, validating its specificity in relation to depression. Hopelessness accounted for a small portion of the variance in SI, compared to demoralization. Formal support for the association of demoralization with SI was provided. Demoralization can improve SB assessment in EDs, particularly among patients whose suicide risk can be unnoticed. Furthermore, demoralization represents a clinically useful concept to increase comprehension of the suffering of the suicidal patient and a possible target for psychotherapeutic interventions.