<b><i>Background and Objectives:</i></b> Changes in cerebral blood flow may play an important role in cognitive impairment among hemodialysis (HD) patients. Physical activity has a promising role in delaying cognitive impairment in general population, but there are only a few studies in HD to confirm this finding. We aimed to evaluate the effects of intradialytic aerobic training on cerebral blood flow and cognitive impairment in HD. <b><i>Design, Setting, Participants, and Measurements:</i></b> This is a pilot, controlled, randomized trial. Fifteen patients underwent intradialytic aerobic training 3 times a week for 4 months. The control group was comprised of another 15 patients. <b><i>Results:</i></b> Trained patients had a statistically significant improvement of cognitive impairment and basilar maximum blood flow velocity. The proportion of arteries with increased flow velocity was statistically significant between groups. <b><i>Conclusions:</i></b> Intradialytic aerobic training improves cognitive impairment and cerebral blood flow of patients in HD, suggesting a possible mechanism improving cognitive impairment by physical training in HD. These data still need to be confirmed by major trials.