Background Bacterial infection is one of the most frequent complications in acute-on-chronic liver failure (ACLF), which leads to high mortality. However, a specific prognostic model for ACLF patients with bacterial infection has not been well established. Aim To establish and validate a nomogram for predicting 30-day mortality of hepatitis B virus-related ACLF (HBV-ACLF) patients with bacterial infection. Methods A total of 513 ACLF patients for HBV reactivation were enrolled in the prospective cohort, and 224 patients with bacterial infection were for derivation. Independent predictors were identified using multivariate logistic model and then assembled into a nomogram to predict 30-day mortality. The performance of the nomogram was assessed based on its calibration, discrimination and clinical utility in a retrospective cohort of 192 HBV-ACLF patients with bacterial infection. Results Age, total bilirubin, lactate dehydrogenase, international normalized ratio and soluble interleukin-2 receptor were shown to be independent risk factors for 30-day mortality of HBV-ACLF patients with bacterial infection and the nomogram was constructed. The nomogram showed a good calibration and discrimination in the derivation cohort, with an area under the receiver operating characteristic curve (AUC) of 0.883. Application of the nomogram in the validation cohort also showed a good calibration and discrimination, with the AUC of 0.852. Decision curve analysis confirmed the clinical utility of the nomogram. Conclusion The nomogram was established and validated for predicting 30-day mortality of HBV-ACLF patients with bacterial infection, which may facilitate optimal therapeutic strategies to improve the prognosis of these patients.