Introduction: In different studies, the effects of exercise and mental stress on electrical waves of the heart have been investigated separately. Nonetheless, the aim of this study was to investigate the simultaneous effect of exercise with mental stress on changes in electrical waves of the heart of young men. Methods: 24 healthy inactive men were selected and randomly divided into two groups of exercise and exercise with mental stress. The subjects in the exercise group biked for 37 minutes (60 % of the maximum aerobic capacity), and the subjects in the exercise with mental stress, biked for 37 minutes while they received 20 minutes of mental stress during biking, from minute 10 to 32. Heart electrocardiogram was recorded at 6 stages of resting, before exercise, 10, 20, 32 and 37 minutes since exercising. Statistical analysis was performed using ANOVA with repeated measures at a significant level of 0.05. Results: No significant difference in heart rate changes (p = 0.71), QRS voltage changes (P = 0.41), QT changes (P = 0.57), QTc changes (P = 0.54) ST segment changes (P = 0.053) and R-R interval changes (P = 0.58) were observed in the interactive effect of group and time. Conclusion: The pattern of changes in the electrical waves of the heart applied in this study was similar in two groups of moderate intensity exercise with mental stress and without mental stress. Keywords: Exercise, Heart, Mental Stress پرونده مقاله