BACKGROUND Modified albumin-bilirubin (mALBI) grade has been established as a survival determinant in hepatocellular carcinoma (HCC) patients who receive locoregional and targeted therapies. OBJECTIVE To investigate whether mALBI could predict survival in unresectable HCC (uHCC) patients who were treated with atezolizumab plus bevacizumab (AB). METHODS A single-center, retrospective cohort study enrolled uHCC patients who received AB treatment between September 2020 and April 2023 and were followed up until June 2023. An association between mALBI and patient survival was determined using Cox proportional hazards analysis. RESULTS Of the 83 patients, 67 patients (80.7%) were male with the mean age of 60.6 years. Among them, 22 patients (26.5%) were classified as Barcelona Clinic Liver Cancer B, and 61 patients (73.5%) were classified as Barcelona Clinic Liver Cancer C. Cirrhosis was present in 76 patients (91.6%), with 58 patients classified as Child-Turcotte-Pugh (CTP) A and 18 as CTP B. The median overall survival (OS) and progression-free survival were 13.0 mo [95% confidence interval (CI): 5.2-20.8] and 9.0 mo (95%CI: 5.0-13.0), respectively. The patients were divided into two groups based on mALBI grades: 42 patients (50.6%) in the mALBI 1 + 2a group; and 41 patients (49.4%) in the mALBI 2b + 3 group. During the median follow-up period of 7.0 mo, the mALBI 1 + 2a group exhibited significantly better survival compared to the mALBI 2b + 3 group, with a median OS that was not reached vs 3.0 mo (95%CI: 0.1-6.0, P < 0.001). In a subgroup of patients with CTP A, the mALBI 1 + 2a group also showed significantly longer survival compared to the mALBI 2b + 3 group, with a median OS that was not reached vs 6.0 mo (95%CI: 3.4-8.6, P < 0.001). In the multivariate analysis, both CTP class and mALBI grade were independently associated with survival, with adjusted hazard ratios (95%CI) of 2.63 (1.19-5.78, P = 0.020) and 3.90 (1.71-8.90, P = 0.001), respectively. CONCLUSIONS mALBI grades can determine survival of uHCC patients receiving AB treatment, particularly those who have mildly impaired liver function. This highlights the importance of assessing mALBI before initiating AB treatment to optimize therapeutic efficacy in clinical practice.