This study tested the assumption that the effectiveness of feedback with regard to performance, motivation, and affect is moderated by the learners' self-concept. A total of 72 sixth-graders completed a web-based interactive learning program. Half of the sample received feedback and the other half received no feedback. Differential feedback effects were detected. For students with a positive academic self-concept, feedback led to a decline in performance and in mood but an increase in effort. With regard to participants with a negative self-concept, feedback worked against the decrease in mood but did not increase performance and motivation. These findings support the claim that feedback effects should be assessed with regard to (1) multiple dimensions and (2) possible moderating variables.