BACKGROUND Our group has shown a positive dose-response in maximal cardiorespiratory exercise capacity (VO(2max)) and heart rate variability (HRV) to 6 months of exercise training but no improvement in VO(2max) for women ≥60 years. Here, we examine the HRV response to exercise training in postmenopausal women younger and older than 60 years. METHODS We examined 365 sedentary, overweight, hypertensive, postmenopausal women randomly assigned to sedentary control or exercise groups exercising at 50% (4 kcal/kg/week, [KKW]), 100% (8 KKW) and 150% (12 KKW) of the National Institutes of Health (NIH) Consensus Development Panel physical activity guidelines. Primary outcomes included time and frequency domain indices of HRV. RESULTS Overall, our analysis demonstrated a significant improvement in parasympathetic tone (rMSSD and high frequency power) for both age strata at 8 KKW and 12 KKW. For rMSSD, the age-stratified responses were: control, <60 years, 0.20 ms, 95% confidence interval (CI)-2.40, 2.81; ≥60 years, 0.07 ms, 95% CI -3.64, 3.79; 4 KKW, <60 years, 3.67 ms, 95% CI 1.55, 5.79; ≥60 years, 1.20 ms, 95% CI -1.82, 4.22; 8-KKW, <60 years, 3.61 ms, 95% CI 0.88, 6.34; ≥60 years, 5.75 ms, 95% CI 1.89, 9.61; and 12-KKW, <60 years, 5.07 ms, 95% CI 2.53, 7.60; ≥60 years, 4.28 ms, 95% CI 0.42, 8.14. CONCLUSIONS VO(2max) and HRV are independent risk factors for cardiovascular disease (CVD) mortality. Despite no improvement in VO(2max), parasympathetic indices of HRV increased in women ≥60 years. This is clinically important, as HRV has important CVD risk and neurovisceral implications beyond cardiorespiratory function.