Despite evidence indicating negative consequences of repetitive head impacts (RHIs) on the brain, the long-term effects remain largely unknown. Contact sports, such as football, expose players to multiple collisions. Professional sports players have undergone thousands of concussive and sub-concussive RHIs over their careers. In this study we used structural 3T MRI to evaluate cortical thickness of 86 former NFL players (mean age ± SD = 54.9 ± 7.9 years old) and 24 former professional non-contact sport athletes as controls (mean age ± SD =57.2 ± 6.9 years old). Cortical thickness was compared between groups using FreeSurfer. The NFL players displayed decreased cortical thickness in the right temporal lobe and fusiform gyrus (cluster-wise p-value=0.0003, 90% CI=0.0001-0.0005) and the left pre- and postcentral gyrus (cluster-wise p-value=0.0096, 90% CI=0.0084-0.0109). When looking only at NFL subjects impaired in measurements of mood and behavior (n=36) compared to controls, NFL players displayed a similar but more extensive cluster of decreased cortical thickness in the right temporal lobe and fusiform gyrus (cluster-wise p-value=0.0001, 90% CI=0.0000-0.0002) and in the left supramarginal gyrus and pre- and postcentral gyrus, (cluster-wise p-value=0.0002, 90% CI=0.0000-0.0004). Reduced cortical thickness in NFL players is suggestive of the long-term effects of RHIs. Still, future studies are necessary for examining the time-course of damage and the implications of regional cortical thinning.