Feedback negativity (FN) is an event-related potential elicited by monetary reward and loss; it is thought to relate to reward-related neural activity and has been linked to depression in children and adults. In the current study, we examined the stability of FN, and its relationship with depression in adolescents, over 2 years in 45 8- to 13-year-old children. From Time 1 to Time 2, FN in response to monetary loss and in response to monetary gain showed moderate to strong reliability (rs = .64 and .67, respectively); these relationships remained significant even when accounting for related variables. FN also demonstrated high within-session reliability. Moreover, the relationship between a blunted FN and greater depression observed at Time 1 was reproduced at Time 2, and the magnitude of FN at Time 1 predicted depressive symptomatology at Time 2. These findings are consistent with the hypothesis that FN and its relationship with depression remain consistent over the course of development, and that FN may prospectively predict later depressive symptomatology. The current results suggest that FN may be suitable as a biomarker of depressive symptoms during adolescence.