Errors are unpredictable events that have the potential to cause harm. The error-related negativity (ERN) is the electrophysiological index of errors and has been posited to reflect sensitivity to threat. Intolerance of uncertainty (IU) is the tendency to perceive uncertain events as threatening. In the present study, 61 participants completed a self-report measure of IU and a flanker task designed to elicit the ERN. Results indicated that IU subscales were associated with the ERN in opposite directions. Cognitive distress in the face of uncertainty (Prospective IU) was associated with a larger ERN and slower reaction time. Inhibition in response to uncertainty (Inhibitory IU) was associated with a smaller ERN and faster reaction time. This study suggests that sensitivity to the uncertainty of errors contributes to the magnitude of the ERN. Furthermore, these findings highlight the importance of considering the heterogeneity of anxiety phenotypes in relation to measures of threat sensitivity.