Respiratory muscle dysfunction after open-heart surgery may influence the cardiopulmonary interactions. The purpose of this study was to examine the correlation between change in the neural respiratory drive (NRD) and change in heart rate variability (HRV) in patients submitted to open-heart surgery. An observational cross-sectional study was conducted among 32 participants. NRD was assessed via a surface electromyogram of the parasternal intercostal muscle (sEMGpara). Polar heart rate monitor was used to measure HRV during the deep breathing maneuver. Evaluations were performed on the day of admission and discharge. There were statistically significant differences in NRD and HRV indices between admission and discharge periods (P<0.05). The difference in peak root mean square of sEMGpara recorded during resting (DeltaRMS sEMGpara tidal), during maximal inspiratory maneuver (DeltasEMGpara max), and its normalized values (DeltaRMS sEMGpara%max) were significantly correlated with the difference in total power (DeltaTotal power), mean of heart rate (DeltaMeanHR), and mean of R to R intervals (DeltaMeanRR) (r=-0.844, P=0.004, r=-0.835, P=0.005, and r=0.643, P=0.043, respectively). It can be concluded that NRD correlated well with HRV in patients who had undergone open-heart surgery.