Postreperfusion significant arrhythmias (PRSA), which is known as part of the diagnostic criteria for postreperfusion syndrome, may serve as a precursor of postreperfusion cardiac arrest (PRCA). Considering the possible relationship between the use of liver grafts with high effluent potassium (eK(+)) concentrations and PRCA, we aimed to investigate the role of eK(+) in PRSA development in deceased liver transplantation (LT). Using the prospectively collected data from a prior observational study, a retrospective study of 91 adult LT recipients with eK(+) measurements between November 2016 and December 2018 was conducted to determine the incidence, predictors, and outcomes of PRSA. PRSA occurred in 46 cases (50.5%), and PRCA occurred in 8 patients (8.8%). Multivariable analysis demonstrated elevated eK(+) concentration before reperfusion (odds ratio [OR], 1.425; 95% confidence interval [CI] 1.134-1.790; P = 0.002), and higher serum potassium level at one minute following reperfusion (sK(1)(+)) (OR, 3.244; 95% CI 1.668-6.380; P = 0.001) as independent risk factors for PRSA. An eK(+) >= 6.9 mmoL/L could predict PRSA with a sensitivity of 71.7% and a specificity of 80.0% (area under the receiver-operating characteristics curve [AUROC], 0.828). In comparison, an sK(1)(+) >= 5.5 mmoL/L could predict PRSA with a sensitivity of 87.0% and a specificity of 64.4% (AUROC, 0.810). PRSA was associated with increased risks of PRCA, postreperfusion vasoplegia, and postoperative early allograft dysfunction. This study has demonstrated that eK(+) has the potential to predict PRSA in deceased LT.