To explore the abnormalities in Iranian athletesʹ electrocardiogram and find any relation with body fat. 239 international athletes were involved in this cross sectional study. Body-fat percentage and resting 12-lead ECGs were recorded from all participants. Of 239 participant athletes, 212 were male and 27 female. 60% of participants had sinus bradycardia. A total of 84% of the athletes demonstrated at least 1 abnormal ECG finding. Average values for the PR, QRS and QT intervals, P-wave duration and QRS axis were in normal range. Frequencies of various ECG abnormal findings in all athletes were as follows: right axis deviation 4.2%, left ventricular hypertrophy 6.2%, sinus arrhythmia 5.8%, right bundle branch block (RBBB) 24.2% (incomplete RBBB 16.8%, complete RBBB 7.4%), ST elevation 72.5%, prolonged QT interval 1.7%, T inversion 3.1% and Mobitz type I 1.2%. The athletesʹ ECG response to treadmill stress test was normal with no ischemia or arrhythmia. The means of BMI and body-fat percentage were 24.04 ± 3.5 kg/m² and 9.15 ± 2.12%, respectively. Pearson correlation coefficient between body-fat percentage and ST changes was 0.65 (P=0.008) in anterior leads and 0.198 (P=0.017) in lateral leads. Also, the correlation coefficient between the body fat percentage and right bundle branch block was 0.36 (P=0.013). The results of current study support the inclusion of ECG in athletesʹ cardiac screening before they engage in vigorous exercises in order to detect the potentially fatal arrhythmias.