Objective: Aerobic exercise on land decreases arterial stiffness, however, the effect of exercise in water on arterial stiffness has not been clear. This study investigated the effect of a 15-min cycling exercise on land and that in water on pulse wave velocity (PWV) as an index of arterial stiffness. Methods: Nine healthy young men were randomly performed exercise on land and exercise in water equivalent to 50% of each maximum oxygen uptake on separate days. The PWV from carotid to femoral artery (aortic PWV) and femoral to posterior tibial artery (leg PWV) were measured at baseline and 15, 30, 60 min after exercise. Results: The heart rate in water was significantly lower during exercise than that on land. In addition, the carbon dioxide output and respiratory exchange ratio during exercise were significantly greater in water. Body temperature increased after the exercise on land but decreased after the exercise in water. Although the aortic PWV and leg PWV decreased concomitantly with decrease in SBP and DBP after the exercise on land, there were no significant changes after the exercise in water. Conclusion: Although acute exercise on land decreased arterial stiffness after exercise, acute exercise in water of the same exercise load did not. The differences in body temperature and blood pressure after exercise may result in diverse arterial stiffness after exercise.