Extensive developmental research has linked peer rejection during adolescence with a host of psychopathological outcomes, including depression. Moreover, recent neuroimaging research has suggested that increased activity in the subgenual region of the anterior cingulate cortex (subACC), which has been consistently linked with depression, is related to heightened sensitivity to peer rejection among adolescents. The goal of the current study was to directly test the hypothesis that adolescents' subACC responses are predictive of their risk for future depression, by examining the relationship between subACC activity during peer rejection and increases in depressive symptoms during the following year. During a functional magnetic resonance imaging scan, 20 13-year-olds were ostensibly excluded by peers during an online social interaction. Participants' depressive symptoms were assessed via parental reports at the time of the scan and 1 year later. Region of interest and whole-brain analyses indicated that greater subACC activity during exclusion was associated with increases in parent-reported depressive symptoms during the following year. These findings suggest that subACC responsivity to social exclusion may serve as a neural marker of adolescents' risk for future depression and have implications for understanding the relationship between sensitivity to peer rejection and the increased risk of depression that occurs during adolescence.