Cardiovascular disease (CVD) is a major cause for a significant proportion of all deaths and disability worldwide. Postoperative renal dysfunction following cardiac surgery is not an uncommon complication of cardiac surgery, which has serious implications with regard to morbidity, mortality, financial expenditure, and resource utilization. This study was performed to compare outcomes of patients with preoperative renal dysfunction with those having normal renal function undergoing off-pump coronary artery bypass grafting (OPCABG). Patients were divided into two categories, depending on their preoperative serum creatinine and glomerular filtration rate (GFR). The preoperative renal dysfunction was defined as serum creatinine >1.3 mg/dL and/or estimated GFR (eGFR) of <60 mL/min/1.73 m2. The category A patients had normal renal function defined as serum creatinine ≤1.3 mg/dL and/or eGFR of ≥60 mL/min/1.73 m2 while the category B patients had preoperative renal dysfunction that did not necessitate renal dialysis. Blood samples were collected from both category patients for serum creatinine prior to surgery, following surgery, on postoperative days 1, 2, 3, 4, 5, and on the day of discharge. The occurrence of acute kidney injury (AKI) was defined as an increase in the serum creatinine levels of ≥0.3 mg/dL within 48 hours or an increase of ≥1.5 above baseline known or presumed to have occurred within the previous 7 days based on Kidney Disease Improving Global Outcomes criteria. This study demonstrated that there was worsening of renal function in 7.4% of patients with normal renal function and 10.74% of patients with renal dysfunction that was not statistically different. Based on the results, we conclude that preoperative renal dysfunction may be a contributing predictor of AKI following OPCABG, and we recommend that the patients with more severe renal dysfunction with eGFR of 45–60 mL/min should be studied to demonstrate this hypothesis.