Traumatic childhood experiences have been found to predict later internalizing problems. This prospective longitudinal study investigated whether repeated and intentional harm doing by peers (peer victimization) in childhood predicts internalizing symptoms in early adolescence. 3,692 children from the Avon Longitudinal Study of Parents and Children (ALSPAC), as well as their mothers and teachers, reported on bullying in childhood (7-10 years) and internalizing problems in early adolescence (11-14 years). Controlling for prior psychopathology, family adversity, gender and IQ, being a victim of bullying was associated with higher overall scores, as well as increased odds of scoring in the severe range (greater than 90th percentile) for emotional and depression symptoms. Victims were also more likely to show persistent depression symptoms over a 2-year period. These associations were found independent of whether mothers, teachers or the children reported on bullying. It is concluded that peer victimization in childhood is a precursor of both short-lived and persistent internalizing symptoms, underlining the importance of environmental factors such as peer relationships in the etiology of internalizing problems.