BACKGROUND:Posttraumatic stress (PTS) results in significant distress or functional impairment. Prevalence studies report higher rates of PTS in forcibly displaced children (FDC). Current evidence deriving mainly from cross-sectional studies is unable to make causal attributions. Given rising rates of forcible displacement reported by the United Nations High Commissioner for Refugees (UNHCR) in 2014, there is increasing need to determine the best policies and practice for engaging mental health needs of FDC. METHODS:This systematic review identifies (1) longitudinal risk and protective factors and correlates for PTS and (2) its natural history in FDC, contributing to research identifying vulnerable subgroups and malleable factors for PTS and understanding its natural history. No meta-analysis was conducted due to heterogeneity; results were analyzed through narrative synthesis. RESULTS:Eleven longitudinal studies were identified. All but one were prospective cohort designs. They identified prevalence rates between 20% and 48.7% at baseline, 10% and 48.3% at 1 year ( k = 7), 18% and 48% at 2-3 years ( k = 2), 8% and 38% at 6 years ( k = 2), and 35% at 12 years using nine measurement methods in seven independent samples. Evidence from multiple associations supported the following risk factors: exposure to traumatic stressors or other stress, older age, and prior psychopathology. Evidence predominantly supported the stability of PTS with some decline. CONCLUSION:While results should be interpreted with caution given small or unrepresentative samples, they suggest regular mental health screenings should be conducted for FDC, who are a vulnerable subgroup with variable onset and remission. Risk associations with prior psychopathology also suggest that screening upon arrival may be advisable for early intervention and prevention.