The in vitro antioxidant effects of petroleum ether, ethyl acetate, and ethanol extracts isolated from Hericium coralloides were investigated. Overall, the ethyl acetate extract of H. coralloides (HcEAE) showed better antioxidant activity in vitro than the petroleum ether and ethanol extracts (HcPEE and HcETE, respectively) of H. coralloides. A comprehensive investigation of the antioxidant activity of the HcEAE in vitro indicated that it possessed superior antioxidant activity, with half maximal inhibitory concentration (IC50) values of 0.93, 1.84, 1.59, and 0.6 mg/mL against DPPH, hydroxyl, ABTS+, and superoxide (O2- ) radicals, respectively. To assess in vivo antioxidant activity, three different doses of HcEAE were orally administered in a D-galactose-induced aged mouse model. Administration of HcEAE significantly increased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and lowered the levels of malondialdehyde (MDA) in brains and sera of mice in a dose-dependent manner. A histopathology assessment indicated that the HcEAE could ameliorate the anile condition of the model mice. These results suggest that the HcEAE has potent antioxidant activity and could minimize the occurrence of age-associated disorders associated with free radicals.