A better understanding of the development of prolonged grief disorder can help professionals identify bereaved in need of intervention efforts and improve the efficiency of services. We aimed to examine the prevalence of and risk factors for prolonged grief disorder in a sample of young, bereaved terrorist attack survivors almost a decade postloss. In total, 165 bereaved survivors (Mage = 27.75, SD = 4.27; 45.5% females) of the 2011 terror attack on Utøya island, Norway, participated in face-to-face, semistructured interviews. At 4-5 months after the attack, early posttraumatic reactions were measured using the Brief Grief Questionnaire, University of California at Los Angeles PTSD Reaction Index, the Hopkins Symptom Checklist-8, and the eight-item Children's Somatic Symptoms Inventory. At 8.5 years postloss, the Traumatic Grief Inventory-Self Report Plus was used to assess prolonged grief disorder. To explore the association between participants' sociodemographic characteristics, early postloss clinical characteristics, and later prolonged grief reactions, we used multiple linear regression analyses. We found that 4.8% of the participants fulfilled the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, text revision diagnostic criteria for prolonged grief disorder 8.5 years after their traumatic loss. Lower age and high levels of early somatic complaints predicted higher prolonged grief reactions almost a decade postloss. Young, bereaved survivors may be at particularly high risk of experiencing persistent grief reactions following the traumatic loss of a peer. Pending replication of our findings, professionals should focus on identifying bereaved who experience intense somatic symptoms early after a traumatic loss. Targeting these symptoms may alleviate the exacerbation of persistent grief reactions several years after a traumatic loss. (PsycInfo Database Record (c) 2024 APA, all rights reserved).