Sports involving repeated head trauma are associated with risk of neurodegenerative disorders such as chronic traumatic encephalopathy (CTE). Among the behavioral manifestations of CTE is increased impulsiveness. Here, the authors investigate the relationship between impulsiveness and exposure to head trauma in a large group of active professional fighters. Fighters tended to report less impulsiveness than did non-fighting control respondents. Overall, greater fight exposure was associated with higher levels of a specific form of impulsiveness, although there were differences between mixed martial arts fighters and boxers. Fight exposure was associated with reduction in volume of certain brain structures, and these changes were also associated with impulsiveness patterns. Longitudinal studies of professional fighters are important to understand the risk for neuropsychiatric problems.