To carry out tasks with the highest possible efficiency we have developed executive mechanisms that monitor task performance and optimize cognitive processing. It has been hypothesized that these executive mechanisms operate even without conscious awareness to maximize their sensitivity to task-relevant outcomes. To test this hypothesis the present study examined the error-related negativity (ERN), an electrophysiological index of the performance-monitoring neural circuitry, during masked visual search. The findings show that representations of target objects that are processed perceptually, but not to the level of awareness, fail to elicit an ERN despite the ability of these targets to elicit a shift of attention. These findings indicate that the performance-monitoring mechanism indexed by the ERN requires target information to be processed to the level of awareness for a mismatch between stimulus and response to be detected.