Cardiotoxicity with potential conduction/structural abnormalities on electrocardiogram (ECG) have been reported with anti-malarial (AM). We aimed to study whether cumulative AM is associated with ECG abnormalities.A standard resting supine ECG was performed on consecutive patients attending the Lupus Clinic since 2012. ECG abnormalities were grouped into structural [left ventricular hypertrophy or atrial enlargement] and conduction abnormalities [prolonged corrected QT interval (QTc), short PR interval, left bundle branch block (LBBB), right bundle branch block (RBBB) and atrioventricular block (AVB), bradycardia, tachycardia, premature atrial complex, ectopic atrial rhythm, atrial fibrillation, premature ventricular complex and ventricular bigeminy]. Associations between cumulative AM and ECG abnormalities (structural or conduction) were assessed using logistic regression analysis (after adjusting for baseline patient characteristics) and in a nested case-control study (1:3).Of 453 patients treated with AM, the median cumulative AM was 1207 grams at ECG. Conduction abnormalities were more prevalent than structural abnormalities, 71 (15.7%) vs. 58 (12.8%). AM cumulative dose did not show a statistical significant association with ECG structural abnormalities, (OR 1.82, p=0.07) while it was protective for conduction ECG abnormalities (OR 0.42, p=0.006). The nested case-control analysis also found that AM cumulative dose is protective against conduction ECG abnormalities (OR 0.36, p=0.0007). SLE duration was a risk factor for both structural and conduction ECG abnormalities.This study suggests an association between cumulative AM dose above the median (1207 g) and structural ECG abnormalities. More importantly, cumulative AM decreases the odds of ECG conduction abnormalities.