Past research provides initial evidence that errors pertaining to undesired (vs. desired) self-standards are of greater motivational significance, but little is known about how quickly people recognize and respond to such errors. To examine immediate responses to errors pertaining to desired and undesired self-standards, we assessed event-related potentials (ERPs) while participants judged self-attributes as personally desirable or undesirable. No discernible differences emerged in ERPs associated with correct responses to undesired compared to desired self-standards. Error-related negativities, shown in past work to index motivational significance, and error positivities, shown in past work to index post-error adjustment, were more pronounced when participants erroneously endorsed undesirable self-standards than when they erroneously failed to endorse desirable self-standards. These electrophysiological correlates of differences in the motivational significance of undesired versus desired self-standards emerged within 400 ms of making an error, suggesting that the impact of these errors does not require extensive deliberation.