Background: We aimed to investigate the neutrophil-lymphocyte ratio (NLR) as a predictor of mortality in patients, who had undergone on-pump and off-pump coronary artery bypass grafting (CABG). Methods: This retrospective study comprised of 457 patients, who underwent CABG (323 on-pump and 134 off pump) between January 2014 and October 2019. Preoperative, postoperative (PO) 1st hour, PO 1st day, and PO 5th day neutrophil-lymphocyte ratios were calculated. The patients were compared, according to demographic, laboratory, and clinical data. A receiver operating characteristics curve was applied to estimate a cut-off value of NLR for mortality. Results: The on-pump group was older (P = 0.001), had a lower Euroscore II (P = 0.036), had a higher graft number (P < 0.001), intensive care unit stay (P = 0.001), and all PO NLRs, except preoperative NLR. There were 14 (3.06%) patients with mortality. Overall (N = 457), PO 1st hour (P = 0.001), PO 1st day (P < 0.001), and PO 5th day (P = 0.016) NLRs were considerably higher in patients with mortality. While none of the NLRs revealed significant difference in the off-pump group, PO 1st hour (P = 0.004) PO 1st day (P 0.001), and PO 5th day (P = 0.007) NLRs were higher in patients with mortality in the on-pump group. The increase in odds ratio of PO NLR was higher in patients with mortality in the overall group of PO 1st day and in the on-pump group of PO 1st hour and PO 1st day. The best combination of sensitivity and specificity was reached at a cut-off value of 6.4 for PO 1st hour NLR and 31.8 for PO 1st day NLR. Conclusions: As in indicator of inflammatory state, NLR readily can be used as a predictor of mortality. Regardless of the CABG technique used, postoperative 1st hour and postoperative 1st day NLR 6.4 and 31.8, respectively, are highly related to mortality.