There is evidence that regular activity can prevent of cardiovascular diseases. There are many reports that exercise and the consumption of olive leaf extract (OLE) have a positive effect on cardiovascular parameters. This study was conducted to compare the effects of exercise and OLE alone and together on electrocardiographic parameters in rats. Materials and Methods: Male Sprague– Dawley rats were randomly divided into six groups (n = 8 rats in each): Control, exercise, OLE (100, 200, and 400 mg/kg, orally for 14 days), and exercise + OLE (200 mg/kg of extract, orally for 14 days). Exercise training in rats was performed using treadmill for 28 days (1 h/day). Electrophysiological parameters including heart rate, PR interval, QT interval, QT corrected (QTc), RR interval, QRS voltage, and duration were obtained from lead II electrocardiogram (ECG) recorded by a PowerLab system. Statistical evaluation was done by one‑ way analysis of variance followed by Fisher’ s least significant difference test and P < 0. 05 was considered statistically significant. Results: The amounts of QT (P = 0. 0009) and QTc interval (P = 0. 0004), RR interval (P < 0. 0001), QRS duration (P = 0. 004), and QRS voltage (P = 0. 003) in the exercise group were significantly higher than those of the control group. However, there were no significant differences in PR interval in comparison with the control group. Exercise (P < 0. 0001) and OLE (400 mg/kg, P = 0. 043) alone and both in combination (P = 0. 007) reduced heart rate and increased the amount of QRS voltage (P = 0. 003, P = 0. 047, and P = 0. 046, respectively) and RR interval (P < 0. 0001, P = 0. 046, and P = 0. 0009, respectively). Conclusion: Results of this study indicated that administration of OLE alone and in combination with exercise has negative chronotropic and positive inotropic effects and also it can prevent of prolongation of QT and QTc interval induced by severe exercise.