A series of experiments were conducted to address the effect of uncertainty regarding performance for predicting the likelihood of a correct-response negativity (CRN) in addition to error-related negativity (ERN). In Study 1, 18 healthy young adults completed letter discrimination tasks during single and dual attention conditions designed to manipulate response certainty. In the second study, the same participants completed easy and difficult tone discrimination tasks designed to influence stimulus certainty. In the third study, task difficulty was manipulated to produce different error rates without altering certainty. Studies 1 and 2 indicated that error and correct responses are processed more similarly when uncertainty is present (i.e., ERN~CRN). Furthermore, uncertainty was associated with attenuation of the ERN and enhancement of the CRN, consistent with an error detection hypothesis. Study 3 indicated that task difficulty alone does not influence the ERN or likelihood of a CRN. These results offer support for the error detection account of the ERN and establish the role of uncertainty in predicting the CRN, as postulated by Scheffers and Coles (2000).