Adaptive decision-making requires that feedback about decision outcomes is adequately processed. Recent studies have shown that fronto-central event-related potentials (ERPs) are sensitive to feedback valence and can be used as an index of feedback processing. The present study investigated whether the processes involved in feedback evaluation are affected by top-down mechanisms driven by knowledge about feedback validity. In a simple decision task, participants had to make use of feedback to learn which one of two stimuli was associated with a reward in a later test phase. Feedback stimuli were followed by a cue indicating whether feedback was valid or invalid. Prior to each block, participants were informed about the frequency of valid feedback in this block. An effect of feedback validity was obtained not only for learning but also for fronto-central ERPs. While high-validity feedback was associated with a fronto-central valence effect, this effect was absent for low-validity feedback. This indicates that processes involved in feedback evaluation are affected by prior knowledge about feedback validity via top-down processes.