--- - |2 Abstract The aim of the current study was to examine whether and how self‐reported decisiveness is associated with response inhibition and performance monitoring. We hypothesized that these two cognitive control mechanisms, both of which are often associated with decision making, would differ in individuals varying in decisiveness. We focused on ERP correlates and behavioral measures of inhibition and error processing in the stop‐signal task. We expected a negative relationship between decisiveness and behavioral measures of inhibitory control. We also hypothesized that stop‐signal‐locked N1 and P3 components and response‐locked error‐related negativity (ERN) would be less pronounced when participants self‐reported higher levels of decisiveness. Correlation analysis identified an association between high decisiveness, long stop‐signal reaction time, and low inhibition rate. Analysis with mixed‐effects linear models revealed that stop signals evoked less pronounced N1 and P3 in individuals scoring higher on decisiveness in both successfully and unsuccessfully inhibited trials. Additionally, high decisiveness was linked to reduced error monitoring, as indicated by decreased ERNs. Importantly, we also found positive association between P3 onset latency and decisiveness, suggesting that individuals scoring higher on this measure have relatively less ability to rapidly engage the stopping process. Thus, our findings primarily indicate that decisiveness is negatively associated with the efficiency of both response inhibition and error monitoring. They also suggest that highly decisive people may share some characteristics of diminished cognitive control with impulsive individuals. - Psychophysiology, Volume 55, Issue 10, October 2018.