Because anxiety disorders appear to follow developmental trajectories that begin early in development, it may be useful to examine the neurodevelopmental correlates of specific cognitive processes that have been linked to anxiety. For instance, the error-related negativity (ERN) is a negative deflection in the event-related potential that is maximal approximately 50 ms following the commission of errors at fronto-central electrode sites, and has consistently been found to be more negative among anxious adults. Much less, however, is known about anxiety and the ERN in children—especially when this relationship develops. We recorded event-related potentials (ERPs) while 55 children aged 8–13 performed an arrow version of the flankers task. Parents and children both reported on children's anxiety. Results suggest that the relationship between the ERN and anxiety changes as a function of age. Among older children, a larger (i.e., more negative) ERN was significantly related to increased anxiety based on parent report. Although the relationship was less robust, the relationship between ERN and anxiety was opposite among younger children. These results are discussed in terms of existing work on anxiety and the ERN, and the need for longitudinal and developmental studies on the relationship between ERN and anxiety.