We assessed the extent to which failures in sustained attention were associated with chronic mild traumatic brain injury (mTBI) deficits in cognitive control among college-age young adults with and without a history of sport-related concussion. Participants completed the ImPACT computer-based assessment and a modified flanker task. Results indicated that a history of mTBI, relative to healthy controls, was associated with inferior overall flanker task performance with a greater number of omission errors and more frequent sequentially occurring omission errors. Accordingly, these findings suggest that failures in the ability to maintain attentional vigilance may, in part, underlie mTBI-related cognition deficits. (Contains 1 table and 1 figure.)