Examining emotion reactivity and recovery following minor problems in daily life can deepen our understanding of how stress affects child mental health. This study assessed children’s immediate and delayed emotion responses to daily problems at school, and examined their correlations with psychological symptoms. On 5 consecutive weekdays, 83 fifth graders (M = 10.91 years, SD = 0.53, 51% female) completed brief diary forms 5 times per day, providing repeated ratings of school problems and emotions. They also completed a one-time questionnaire about symptoms of depression, and parents and teachers rated child internalizing and externalizing problems. Using multilevel modeling techniques, we assessed within-person daily associations between school problems and negative and positive emotion at school and again at bedtime. On days when children experienced more school problems, they reported more negative emotion and less positive emotion at school, and at bedtime. There were reliable individual differences in emotion reactivity and recovery. Individual-level indices of emotion responses derived from multilevel models were correlated with child psychological symptoms. Children who showed more negative emotion reactivity reported more depressive symptoms. Multiple informants described fewer internalizing problems among children who showed better recovery by bedtime, even after controlling for children’s average levels of exposure to school problems. Diary methods can extend our understanding of the links between daily stress, emotions and child mental health. Recovery following stressful events may be an important target of research and intervention for child internalizing problems.