© 2015 Taylor and Francis. Introduction: Cognitive impairment is a highly prevalent, disabling, and poorly managed consequence of multiple sclerosis (MS). Exercise training represents a promising approach for managing cognitive impairment in this population. However, there is limited evidence supporting an optimal exercise stimulus for improving cognition in MS. The current study compared the acute effects of moderate-intensity treadmill walking, moderate-intensity cycle ergometry, and guided yoga with those of quiet rest on executive control in 24 persons with relapsing-remitting MS without impaired cognitive processing speed using a within-subjects, repeated measures design. Method: Participants completed four experimental conditions that consisted of 20 minutes of moderate-intensity treadmill walking exercise, moderate-intensity cycle ergometer exercise, guided yoga, and quiet rest in a randomized, counterbalanced order. Participants underwent a modified-flanker task as a measure of executive control immediately prior to and following each condition. Results: Repeated measures analyses of variance (ANOVAs) indicated general pre-to-post improvements in reaction time, but not accuracy, on the modified-flanker task for all three exercise modalities compared with quiet rest. However, there were additional, selective pre-to-post reductions in the cost of interfering stimuli on reaction time on the modified-flanker task for treadmill walking, F(1, 23) = 4.67, p =.04, ηp2 =.17, but not cycle ergometry, F(1, 23) = 0.12, p =.73, ηp2 <.01, or guided yoga, F(1, 23) = 0.73, p =.40, ηp2 =.03, compared with quiet rest. Conclusions: The present results support treadmill walking as the modality of exercise that might exert the largest beneficial effects on executive control in persons with relapsing-remitting MS without impaired cognitive processing speed. This represents an exciting starting point for delineating the appropriate exercise stimulus (i.e., modality and intensity) for inclusion in a subsequent longitudinal exercise training intervention for improving cognitive performance in this population.