BackgroundIn 2014, the terrorist militant group the Islamic State of Iraq and Syria (ISIS) took over one-third of Iraq. This study measured the rate of posttraumatic stress disorder (PTSD) among Iraqi internally displaced persons (IDPs) and examined associated demographic and traumatic risk factors and comorbid psychiatric symptoms.MethodsA cross-sectional survey was carried out in April-June 2015 at the Khanke camp, northern Iraq. Trauma exposure and PTSD were measured by the Harvard Trauma Questionnaire (Iraqi version), and psychiatric comorbidity was measured by the General Health Questionnaire (GHQ-28).ResultsOf 822 adult IDPs, 33.8% screened positive for PTSD. Associated factors included exposure to a high number of traumatic events, unmet basic needs and having witnessed the destruction of residential or religious areas. Being a widow was the only linked demographic factor (OR = 14.56, 95% CI: 2.93–72.27). The mean scores of anxiety/insomnia and somatic symptoms were above the average cutoff means (M = 3.74, SD = 1.98, R = 0–7 and M = 3.69, SD = 2.14, R = 0–7, respectively) among the IDPs with PTSD.ConclusionsHigh traumatic exposure, specifically unmet basic needs and having witnessed destruction, was an important predictor of PTSD among IDPs. Psychiatric comorbidity was high among those with PTSD. Anxiety, insomnia and somatic symptoms were strongly associated with PTSD. These findings are important for mental health planning for IDPs in camps.Clinical trial registrationNot applicable.