Reduced heart rate variability (HRV) in older patients with heart failure (HF) is common and indicates poor prognosis. Exercise training (ET) has been shown to improve HRV in younger patients with HF. However, the effect of ET on HRV in older patients with HF is not known. Sixty-six participants (36% men), aged 69+/-5 years, with HF and both preserved ejection fraction (HFPEF) and reduced ejection fraction (HFREF), were randomly assigned to 16 weeks of supervised ET (ET group) vs attention-control (AC group). Two HRV parameters (the standard deviation of all normal RR intervals [SDNN] and the root mean square of successive differences in normal RR intervals [RMSSD]) were measured at baseline and after completion of the study. When compared with the AC group, the ET group had a significantly greater increase in both SDNN (15.46+/-5.02 ms in ET vs 2.37+/-2.13 ms in AC, P=.016) and RMSSD (17.53+/-7.83 ms in ET vs 1.69+/-2.63 ms in AC, P=.003). This increase was seen in both sexes and HF categories. ET improved HRV in older patients with both HFREF and HFPEF.