Objective: Acute kidney disease develops 16% - 30% of patients with preoperative impaired renal functions. Our aim of this study was to compare postoperative renal outcomes using two open heart surgery techniques, on-pump beating heart (OPBH) and conventional on-pump (COP), in patients who have preoperative low glomerular filtration rate (eGFR) as an indicator of creatinine clearance. Methods: From 2004 to 2015, 341 patients with preoperative creatinine clearance were lower than 90 ml/min/1.73m2 were selected for this study. On-Pump beating heart was performed in 111 patients (Group I). Conventional on-pump technique was used in 200 patients. In the remaining patients, we measured postoperative Tumor Necrosis Factor Alpha (TNF-alpha), cardiac troponin I (cTn-I), Brain natriuretic peptid (NT-Pro- BNP), creati-nine (Cr), blood urea nitrogen (BUN) and postoperative eGFR daily until day four after surgery. Results: There were no differences in baseline levels of TNF-alpha, NT-Pro-BNP, BUN, cTn-I, Cr levels between the groups. Cardiopulmonary bypass (CPB) time were much longer and cumulative inotrope use was significantly higher in patients underwent COP (P < 0.05). Postoperative TNF-alpha and c-TnI was signifi-cantly higher in group II (P < 0.001). In group II, blood urea nitrogen and creatinine levels were high significantly (P < 0.001). Three patients in Group I (2.7%), and 6 patients (6.2%) in Group II required hemodialyses after surgery. Data revealed all-cause survivals at 1 and 24 months of 88% and 75% for OPBH versus 78% and 59% for COP technique (P = 0.021; P = 0.034). In a comorbidity adjusted Cox model, OPBH was associated with a 22% reduction in all-cause morbidity (P = 0.03). Conclusion: Our study showed that on-pump beating heart CABG technique provides a morbidity benefit and is associated with a lower risk of peroperative LOS in patients with mild renal disfunction. Our study results suggest that OPBH is superior to the COP in terms of postoperative renal injury and cardiac mediators.