Background/Objectives: Antrodia camphorata, also known as “Niuchangchih” in Taiwan, is a unique medicinal mushroom native to Taiwan. It is used in traditional medicine to treat various health conditions. In this study, we investigated the efficacy of A. camphorata mycelia on alcohol-induced liver damage, both in vitro and in vivo, in a Good Laboratory Practice (GLP) facility. Methods: The experimental groups consisted of a normal control group (G1), a negative control group (G2), an A. camphorata mycelium powder 50 mg/kg/day administration group (G3), a 100 mg/kg/day administration group (G4), a 200 mg/kg/day administration group (G5), and a positive control silymarin 200 mg/kg/day administration group (G6), with 10 Sprague Dawley rats assigned to each treatment group. Results: We found that treatment with A. camphorata mycelium powder significantly reduced alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, cholesterol, adiponectin, triglyceride, and malondialdehyde concentrations. Histopathological analysis also revealed that the inflammation score significantly decreased in the A. camphorata-treated groups. Conclusion: Based on these results, we conclude that repeated oral administration of A. camphorata mycelium powder is effective in improving alcoholic liver disease.