Performance monitoring tasks are suitable for investigating aging-related decline in executive functions. However, little is known about performance monitoring in premature pathological aging and mild cognitive impairment (MCI). This study recorded the error-related negativity (ERN) and the correct-related negativity (CRN) as indices of performance monitoring and compared these responses in older adults with MCI to the ones of younger and older adult controls. No differences in either ERN or CRN were found between younger and older adult controls. Compared to both control groups, we observed a more negatively pronounced CRN in MCI subjects. Only in this group did the amplitude of the CRN not differ from the one of the ERN. In general, larger differences between both components (i.e., ERN > CRN) were associated with better performances in cognitive tests requiring inhibition and executive control. These results indicate that electrophysiological correlates of performance monitoring (ERN and CRN) are differentially affected by aging and MCI.