We investigated the impact on survival of modified albumin-bilirubin (mALBI) grade versus Child-Pugh classification in patients with hepatocellular carcinoma (HCC) who received lenvatinib. A total of 524 patients with HCC who received lenvatinib were included. Univariate analysis showed that mALBI grade 2b/3 and Child-Pugh class B/C were significantly associated with survival [hazard ratio (HR), 2.471; 95% confidence interval (CI), 1.944-3.141 and HR, 2.178; 95%CI, 1.591-2.982]. In patients with a Child-Pugh score of 5, multivariate analysis showed that mALBI grade 2b/3 was independently associated with survival (HR, 1.814; 95%CI, 1.083-3.037). Conversely, among patients with mALBI grade 1/2a, there was no difference in survival between those with a Child-Pugh class of 5 or 6 (p = 0.735). Time-dependent receiver operating characteristic analysis showed that the ALBI score predicted survival better than the Child-Pugh score. The optimal cut-off value of the ALBI score for predicting survival was nearly the same as the value separating mALBI grades 2a and 2b. In conclusion, the mALBI grade was a better predictor of survival than the Child-Pugh classification in patients with unresectable HCC who received lenvatinib therapy.