AbstractMillions of people are currently displaced. About half of them are children who are at increased risk of mental health problems. While some risk factors such as war exposure are well established, less is known regarding the effects of the local refugee environment. Here we show that the prevalence and comorbidity of mental health problems in Syrian refugee children living in settlements in Lebanon are high. We assessed individual, familial and social factors in a prospective cohort study (N = 1,591 child–caregiver dyads interviewed between October 2017 and January 2018; n = 1,000 interviewed at 1 yr follow-up). Of these children, 39.6% met the criteria for post-traumatic stress disorder, 26.9% for conduct/oppositional defiant disorder, 20.1% for depression and 47.8% for anxiety disorders. Exposure to daily stressors was the factor most strongly associated with children’s mental health problems. Interventions and policies addressing ongoing daily stressors are as important as scaling up mental health services for refugee families.