Background The identification of patients at high risk of developing postoperative complications is important to improve surgical safety. We sought to develop an individualized tool to predict post-hepatectomy major complications in hepatitis B virus (HBV)-infected patients with hepatocellular carcinoma (HCC). Methods A multicenter database of patients undergoing hepatectomy for HCC were analyzed; 2/3 and 1/3 of patients were assigned to the training and validation cohorts, respectively. Independent risks of postoperative 30-day major complications (Clavien-Dindo grades III-V) were identified and used to construct a web-based prediction model, which predictive accuracy was assessed using C-index and calibration curves, which was further validated by the validation cohort and compared with conventional scores. Result Among 2762 patients, 391 (14.2%) developed major complications after hepatectomy. Diabetes mellitus, concurrent hepatitis C virus infection, HCC beyond the Milan criteria, cirrhosis, preoperative HBV-DNA level, albumin-bilirubin (ALBI), and aspartate transaminase to platelet ratio index (APRI) were identified as independent predictors of developing major complications, which were used to construct the online calculator. This model demonstrated good calibration and discrimination, with the C-indexes of 0.752 and 0.743 in the training and validation cohorts, respectively, which were significantly higher than those conventional scores (the training and validation cohorts: 0.565 similar to 0.650 and 0.568 similar to 0.614, all P < 0.001). Conclusions A web-based prediction model was developed to predict the probability of post-hepatectomy major complications in an individual HBV-infected patient with HCC. It can be used easily in the real-world clinical setting to help management-related decision-making and early warning, especially in areas with endemic HBV infection.