Research on the acute effects of exercise on cognitive performance by older adults is limited by a focus on nonhealthy populations. Furthermore, the duration of cognitive improvements after exercise has not been examined. Thus, this study was designed to test the immediate and delayed effects of acute exercise on cognitive performance of healthy older adults. Cognitive performance was assessed using the Stroop task. Participants were randomly assigned to an exercise (20 min of walking) or control (sitting quietly) condition. The Stroop task was administered at baseline and at 12 time points after treatment. Acute exercise resulted in better Stroop test performance immediately postexercise; however, the effects were limited to the color test. No effects of exercise on performance were observed for the Stroop interference or inhibition tests. Findings suggest that acute exercise performed by healthy older adults has short-term benefits for speed of processing but does not affect other types of cognitive functioning.