Approach, avoidance and the supervisory control system are fundamental to human behavior. Much past research has examined the neurophysiological models relating trait approach and avoidance. Using measures of electroencephalographic (EEG) frontal asymmetry, trait approach has been associated with greater left-frontal activity and trait avoidance has been associated with greater right-frontal activity. However, traits related to the supervisory control system have not been previously associated with frontal asymmetry. The current study sought to test whether trait positive urgency, measuring the tendency towards rash action in response to extreme positive emotional states, would relate to frontal alpha asymmetry. One hundred twenty-six individuals completed a measure of positive urgency and resting EEG recordings. Greater positive urgency was associated with greater relative left-frontal EEG activity. Source localization revealed that this relationship appeared to originate from reduced right-frontal activity in the inferior frontal gyrus. These results clarify that the link between frontal asymmetry and positive urgency is related to reduced right-frontal activity. Reduced right-frontal activity may be a potential neurobiological trait related to the supervisory control system.