Objective To investigate the effect of pre-transplant metabolic syndrome (MS) on new-onset postoperative atrial fibrillation (POAF) in adult liver transplant recipients.Methods Adult patients (age ≥18 years) who underwent primary liver transplantation at the UCLA Medical Center between January 2009 and December 2015 were retrospectively reviewed.Clinical data were collected after obtaining institutional review board approval.MS was defined according to the 2009 harmonized definition.POAF was defined as new-onset atrial fibrillation within 30 days after liver transplantation in patients without chronic persistent atrial fibrillation.Patients were divided into two groups:MS and non-MS groups.Incidence of POAF was compared between two groups.Then,univariate and multivariate logistic regression analyses were performed to assess the relationships between MS and POAF.Results Of 842 patients,prevalence of pre-transplant MS was 29.4％.POAF occurred in 71 patients (8.4％).The incidence of POAF between MS and non-MS groups significantly differed (14.6％ vs.5.9％,P＜0.01).The logistic regression analysis revealed that the presence of MS was significantly associated with POAF [odd ratios (OR) 2.290,95％ CI 1.342-3.907].Other risk factors include recipient age,prior history of AF,and preoperative baseline creatinine (OR 1.030,2.479 and 1.380,respectively,all P＜0.05).Conclusion The presence of pre-transplant MS is an independent risk factor for POAF in liver transplantation patients.Pre-transplant MS should be properly diagnosed and managed before transplantation.