Background: Preoperative anemia is associated with increased morbidity and mortality after cardiac surgery, so we investigated the effect of preoperative hemoglobin levels on early outcome of coronary artery bypass grafting (CABG). Patients & Methods: This retrospective study included (782 cases) all patients underwent CABG, except those with the exclusion criteria (patients with preoperative heart failure, renal impairment, chronic liver disease or chronic obstructive pulmonary diseases), during a duration of 4 years from 1st of June 2013 till 31th of May 2017 in the department of cardiothoracic surgery at Zagazig University Hospitals. Anemia was defined as hemoglobin >12.0 g/dL in women and >13.0 g/dL in men. The items we focused on during the study were: ICU stay duration, post-operative bleeding, sternal wound infection, myocardial infarction, hospital stay duration and in-hospital mortality. Results: Our study reported that: the group with preoperative anemia was associated with increased incidence of adverse events more than the group with normal preoperative hemoglobin levels. The concluded results showed that: percentage of patients who suffered from prolonged ICU stay were (59.8% vs. 29.8%), post-operative bleeding (88.0% vs. 54.9%), sternal wound infection (6.0% vs. 2.8%), myocardial infarction (3.9% vs. 2%), prolonged hospital stay (61.5% vs. 31.8%) and in-hospital mortality (7.7% vs. 4%) among the anemic and normal group respectively. Conclusions: Preoperative anemia is associated with a significantly increased risk of post-operative morbidity and mortality.