This study investigues the chemical composition of the mushroom Agaricus brasiliens is prepared in different commercially available forms: dehydrated whole mushrooms, mushroom powder, and capsules. The most active form was subsequently examined in vivo to investigate its possible effects on liver tissue. For the in vitro assay, the antioxidant potential via DPPH radical and hypocholesterolemic through the activity of HMG-CoA reductase were analyzed. Regarding the in vivo test, 24 female albino Fischer rats (aged 80–95 days; average weight, 205 g) were fed either the AIN-93M modified standard diet (C) or a hypercholesterolemic dietcontaining 25 % soybean oil and 1 % cholesterol supplemented with mushroom powder (HAb) or simvastatin (HS). Animals received the diets for 8 weeks. After this period, the liver was separated for histopathological analysis. Their nutritional components were compared, as well as the antioxidant activity (DPPH free radical assay) and 2-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitory effect. All samples showed high contents of fiber and protein, plus low levels of lipid (1–2%) except for the capsule form (10.3%). They all inhibited 2,2-diphenyl-1-picrylhydrazyl free radicals to a large extent (70–83%), thus demonstrating high antioxidant activity. Chemical characterization using HPLC revealed that tocopherol in dehydrated whole A. brasiliensis is a potent antioxidant and quenches the reactive oxygen species. The ethanolic extracts of samples were found to efficiently inhibit HMG-CoA reductase expression. Significant changes were observed in the liver tissue of animals that had Agaricus brasiliensis and Simvastatin added to their diet. Our results, taken together, confirm the significant presence of bioactive compounds in Agaricus brasiliensis, reflecting its ability to act as a food with functional properties. These results reinforce the importance of complementary studies to evaluate the conditions of cultivation and obtainment of the bioactive compounds and their possible interference in the composition and, consequently, in the biological activity of Agaricus brasiliensis.