AbstractStructural and functional alterations in a variety of brain regions have been associated with depression and risk for depression across the life span. A majority of these regions are associated with emotion reactivity and/or regulation. However, it is generally unclear what mechanistic role these alterations play in the etiology of depression. A first step toward understanding this is to characterize the relationships between variation in brain structure/function and individual differences in depression severity and related processes, particularly emotion regulation. To this end, the current study examines how brain structure and function predict concurrent and longitudinal measures of depression symptomology and emotion regulation skills in psychiatrically healthy school-age children (N = 60). Specifically, we found that smaller hippocampus volumes and greater responses to sad faces in emotion reactivity regions predict increased depressive symptoms at the time of scan, whereas larger amygdala volumes, smaller insula volumes, and greater responses in emotion reactivity regions predict decreased emotion regulation skills. In addition, larger insula volumes predict improvements in emotion regulation skills even after accounting for emotion regulation at the time of scan. Understanding brain–behavior relationships in psychiatrically healthy samples, especially early in development, will help inform normative developmental trajectories and neural alterations in depression and other affective pathology.