Background: Impaired cardiac performance is a frequent presentation after Coronary Artery Bypass Graft (CABG) surgery. Intra-Aortic Balloon Pump (IABP), as a mechanical support, is lifesaving in many cases of low cardiac output state. IABP is needed to be in place from a few hours to a few days. Weaning is usually done according to patients' hemodynamic response. Up to now, many studies have addressed the withdrawal methods, but few are related to predict the support time. Objectives: This study aimed to evaluate whether high serum lactate levels are early predictors of IABP dependency after CABG surgery. Patients and Methods: This prospective cohort study was performed on 843 patients who underwent CABG surgery from April 2009 to January 2014 in Pars hospital. Among these patients, 47 ones required IABP support and were all entered into our study. Arterial blood samples were collected by 2-hour intervals during the first 12 hours after the operation. Serum lactate levels were compared according to IABP dependency. The data were analyzed using chi-square, t-test, and correlation coefficient and α = 0.05 was considered to be the significance level. Results: Based on the results, 97.8% of the patients (n = 46) were successfully weaned from IABP support and 95.7% (n = 45) survived to discharge from the hospital. Two patients with persistent serum lactate levels > 15 mmol/L in the first 12 hours of IABP support had the worst prognosis. A significant association was found between the mean serum lactate levels ≥ 6 mmol/L in the first 12 hours after the surgery and ≥ 48 hours dependency on IABP (P = 0.030). Conclusions: Prediction of IABP dependency may be possible by measuring serum lactate levels in the first 12 hours after CABG surgery.