PURPOSE: The war in Syria has created the greatest refugee crisis in the twenty-first century. Turkey hosts the highest number of registered Syrian refugees, who are at increased risk of common mental disorders because of their exposure to war, violence and post-displacement stressors. The aim of this paper is to examine the prevalence and predictors of anxiety, depression, and post-traumatic stress disorder (PTSD) symptoms among Syrian refugees living in Turkey. METHODS: A cross-sectional survey of adult Syrian refugees was conducted between February and May 2018 in Istanbul (Sultanbeyli district). Participants (N = 1678) were randomly selected through the registration system of the district municipality. The Hopkins Symptoms Checklist (HSCL-25) was used to measure anxiety and depression and the Posttraumatic Stress Disorder (PTSD) Checklist (PCL-5) assessed posttraumatic stress. Descriptive and multivariate regression analyses were used. RESULTS: The prevalence of symptoms of anxiety, depression and PTSD were 36.1%, 34.7% and 19.6%, respectively. Comorbidity was high. Regression analyses identified several socio-demographic, health and post-displacement variables that predicted common mental disorders including: being female, facing economic difficulties, previous trauma experience, and unmet need for social support, safety, law and justice. A lifetime history of mental health treatment and problems accessing adequate healthcare were associated with depression and anxiety but not with PTSD. CONCLUSIONS: Mental disorder symptoms are highly prevalent among Syrian refugees in Turkey. The association with post-displacement factors points to the importance of comprehensive health and social services that can address these social, economic and cultural stressors.