Grief is a normal human response to the death of a loved one that may vary among individuals and in the way it manifests itself across cultures. Whereas the majority of bereaved people adjust adequately to the loss, a small but noteworthy proportion of individuals may experience a prolongation of the symptoms of acute grief well beyond the period when these have commonly abated. This syndrome, characterised by prolonged psychological distress in relation to bereavement, has been termed prolonged grief (PG) and shows distinct psychopathological features compared with other stress-related mental disorders. Accurately diagnosing PG in the context of difficult bereavement is an ongoing challenge to clinicians and researchers and many have called for improving the identification of PG and its treatment. PG has been recognised as a predictor of negative outcomes, such as substantial impairment in work and social functioning, reduction of quality of life, risk for mental disorders and suicidality, and physical health problems. This article discusses the main clinical features of PG, the determinants associated with the severity of PG symptoms, the risk factors that may predispose an individual to develop PG and the efficacy of different preventive and treatment approaches, including psychopharmacological and psychotherapeutic interventions.