This study extracted the error-related negativity (ERN) waveform component recorded from a visual-spatial attention and a visual short-term memory task to assess rigorously the long-term and cumulative effects of concussions on evaluative processes of cognitive control related to performance monitoring. This study demonstrates that, relative to control athletes, multiply concussed athletes show significant ERN amplitude reduction elicited by error generation. These cumulative effects of concussions on ERN amplitude were found in two distinct experimental paradigms designed to solicit concussion-sensitive cognitive abilities such as attention and short-term memory. This suggests that the mechanisms that contribute to the evaluation of cognitive performance may be significantly affected following multiple concussions even in low-conflict situations.