An electrocardiogram (ECG) leads physicians to diagnose many potentially life-threatening cardiac, metabolic, electrolyte, and toxicological conditions.This study was designed to evaluate the competency of emergency medicine residents (EMRs) in comparison with cardiologists in the interpretation of ECG when an interpretation checklist is used.This clinical trial was done in the emergency wards of the first grand general hospital of Iran. Patients were categorized in three classes of disorder severity based on ECG abnormalities. The two stages of the study included the survey phase (Stage I), training phase and intervention phase (Stage II). Accuracy of ECG interpretation by EMRs and cardiologists was compared before and after using a Daily ECG Check List (DECKList). One hundred and fifty ECGs were evaluated in Stage I, before DECKList usage, and 150 ECGs were evaluated in stage II, after DECKList usage by EMRs. Mean age of participants was 60.13 years in Stage I and 61.66 years in Stage II. Stage I and II were similar to each other in terms of disorder severity (P=0.22). Mean the ECG interpretation score was significantly different between Stages I and II (P<0.001). Concordance of ECG diagnosis between EMRs and cardiologists was significantly different in Stages I and II (P<0.01). In first-year EMRs, ECG diagnosis scores in stages I and II were not changed significantly. However, ECG interpretation scores increased significantly in first-year EMRs (P=0.04). In second-year EMRs, both ECG interpretation and ECG diagnosis scores improved significantly (P<0.05 and P<0.01, respectively). In third year EMRs, ECG interpretation was not improved but ECG diagnosis based on two methods improved significantly (P<0.05).The significant increase in accuracy of ECG interpretation and final diagnosis can be attributed to the utilization of a checklist by EMRs especially in the first year and second residents.