Key PointsQuestionsHow does emotional distress change longitudinally in unaccompanied migrant children and adolescents predominantly from the Northern Triangle of Central America, and what characteristics are associated with emotional distress?FindingsThis cohort study of 176 unaccompanied migrant children and adolescents showed that most, particularly girls, report high rates of persistent emotional distress. Girls were more likely than boys to have increased severity of emotional distress at follow-up.MeaningResults suggest that unaccompanied migrant children and adolescents, particularly girls, are at high risk for emotional distress that persists after resettlement in the US.