In this paper, we contend that complicated grief (CG) constitutes a distinct psychopathological diagnostic entity and thus warrants a place in standardized psychiatric diagnostic taxonomies. CG is characterized by a unique pattern of symptoms following bereavement that are typically slow to resolve and can persist for years if left untreated. This paper will demonstrate that existing diagnoses are not sufficient, as the phenomenology, risk factors, clinical correlates, course, and outcomes for CG are distinct from those of posttraumatic stress disorder (PTSD), major depressive disorder (MDD), and adjustment disorder (AD). It is argued that the establishment of CG as a diagnostic entity is essential because its symptoms are associated with enduring mental and physical health morbidity and require specifically designed clinical interventions. We conduct a critical review of all published evidence on this topic to date, demonstrating that the advantages of standardizing the diagnostic criteria of CG outweigh the disadvantages. In addition, recommendations for future lines of research are made. This paper concludes that CG must be established in the current nosology to address the needs of individuals who are significantly suffering and impaired by this disorder.