Atrial fibrillation (AF) is the most common arrhythmia after cardiothoracic surgery. AF following coronary artery bypass graft (CABG) is associated with an increase in morbidity, mortality, hemodynamic instability, thromboembolic events, severity of heart failure and ICU and hospital stay. Corticosteroids have a variety of beneficial effects on recovery after elective surgery. This study was designed to test the hypothesis that low dose of Methylprednisolone (MP) can affect post-CABG AF and early complications in patients with severe left ventricle dysfunction who underwent elective off-pump coronary artery bypass. A total of 120 patients with LV dysfunction undergoing elective off- pump CABG randomly received either MP or placebo. Diabetic patients and those who were receiving corticosteroids were excluded. The MP group received 5mg/kg of MP intravenously after induction of anesthesia and the placebo group received an equal volume of normal saline. We evaluated Post-CABG variables including incidence, duration and frequency of AF recurrence and early morbidity such as bleeding, infection, vomiting, renal and respiratory dysfunctions, ICU or hospital stay and early mortality. The mean age of patients was 62.11 ± 12.34 years with the 2.4 male to female ratio. AF occurred in 23(19.2%) patients. No significant difference in the incidence of new AF was found between the placebo (21.7%) and MP group (16.7%) (P=0.47). MP did not affect postoperative bleeding, infection, vomiting, renal and respiratory dysfunction and mortality; however, MP significantly reduced ICU and hospital length of stay. MP did not affect the incidence, duration and frequency of AF recurrence in patients with severe LV dysfunction undergoing off-pump CABG. However, MP could reduce ICU and hospital stay significantly in these patients.