Acute systemic thermal therapy can improve arterial stiffness in both animals and humans. We examined and compared the effects of acute local thermal therapy (footbath) on an indicator of human arterial stiffness, cardio-ankle vascular index (CAVI), in 16 healthy young (29.4 ± 0.4 years) and 16 older (59.8 ± 1.7 years) women. Measurements were made at baseline (BL) and at 0 and 30 min after footbath in footbath trial, and at corresponding time points without footbath in control trial. In the footbath trial, subjects immersed their lower legs and feet in water for 30 min, with water temperature ranging from 41 to 43°C. The results showed that footbath elicited significant reductions in CAVI at 0 min compared to the same trial's baseline in both young and older groups (0.55 ± 0.07, P = 0.01 for young; 0.42 ± 0.15, P = 0.03 for older, respectively) with no changes found in the control trials. The percentage of CAVI change at 0 min was significantly greater in young women (91.9 ± 1.1%) compared to older women (96.5 ± 1.8%, P < 0.05). This study indicated that acute warm footbath results in transient improvement of systemic arterial stiffness in both healthy young and older women. Despite similar intervention, the percentage response of arterial stiffness to footbath was attenuated in older women.