Background: ABO-incompatible liver transplantation (ABO-i LT) is being increasingly used for end-stage liver disease patients with limited donor options. Advances in preoperative techniques like plasma exchange, along with improved postoperative immunosuppression, have enhanced outcomes. However, higher intraoperative transfusion during ABO-i LT can increase complications including acute kidney injury more, compared to ABO-compatible transplant. Our study aims to assess early postoperative complications within a year according to the intraoperative transfusion volume in ABO-i LT. Methods: We reviewed electronic medical records of adult patients undergoing ABO-i LT at Seoul National University Hospital between July 2013 and June 2018, excluding patients with prior transplants. Demographics variables, comorbidities, preoperative factors, surgical details, and postoperative outcomes were collected. The primary outcome was early postoperative immunologic complication (biliary complications and acute cellular rejection within a year), according to intraoperative red blood cell (RBC) transfusion. Results: During the period, 75 patients received ABO-i LT and there was no case of re-transplantation. Among 75 patients, 47 received ≤4 units and 28 received >4 units of packed RBCs during surgery. Baseline characteristics were similar, except for some transplant-related factors such as cause of transplant, Model for End-stage Liver Disease or Child-Pugh score. RBC transfusion more than 4 units was associated with longer cold ischemic time, higher estimated blood loss, and lower preoperative and intraoperative hemoglobin levels. Regarding early postoperative complications, the incidence of acute cellular rejection risk was significantly higher in RBC ≤4 units group (14 [29.8%] vs. 2 [7.1%], P=0.021). Biliary complications trended higher in the >4 units group, though statistically insignificant. Other outcomes are shown in Table. However, univariate and multivariate logistic analysis showed that the volume of transfusion was not associated with the increased risk of biliary complications. Conclusions: Intraoperative RBC transfusion (>4 units) was not associated with early biliary complications after ABO-i LT, but it significantly associated with higher acute cellular rejection.