Hepatitis often occurs after initiating immune checkpoint inhibitor (ICI) treatment. The time and grade of hepatitis after ICI starts and the prognostic role of immune-related hepatitis in patients with advanced hepatocellular carcinoma (aHCC) remain unclear. In this real-world analysis, we enrolled aHCC patients receiving ICIs, documented the highest level of liver enzymes during/after ICIs, and analyzed the survival impact of different hepatitis patterns. One hundred and ninety-three aHCC patients receiving ICIs were recruited. During ICIs, 88.6% of patients experienced aspartate transaminase (AST) elevations (Grade III/IV: 7.8%). For alanine transaminase (ALT), 81.3% had elevated levels (Grade III/IV: 3.6%), and 41.5% of patients had elevated bilirubin levels (Grade 3/4: 6.7%). The median AST, ALT, and total bilirubin values significantly increased after ICI treatment initiated (all p < 0.001) and, similarly, after excluding progressive disease (p = 0.014, p = 0.002, p < 0.001). The median time of hepatitis occurrence is from the 4.0th to 15.9th weeks. Multivariable analysis showed that patterns of liver enzyme change of AST and total bilirubin in patients receiving ICIs significantly correlate to overall survival (OS, p = 0.009 and 0.001, respectively). After ICI termination, patients with elevated bilirubin (p = 0.003) and AST (p = 0.005) would indicate poor survival, with adjustment of viral hepatitis and ICI responses. Hepatitis emerges between the 4th and 20th weeks post-ICI initiation. Changes in liver enzymes during ICI therapy do not directly affect OS, implying the safety of ICI use when corticosteroids are promptly administered if clinically indicated.