The antioxidant capacity of Fomitopsis pinicola extracts was determined based on DPPH radical scavenging activites. Their total phenolic and flavonoid contents were also investigated. Antioxidant enzymes are important in controlling oxidative stress and maintaining cellular homeostatis. They can protect cells from the deleterious effects of reactive oxygen species and prevent the development of degenerative diseases such as Alzhemier disease, Parkinson disease, cancer, and even aging. In this regard, the modulatory activities of F. pinicola extracts on the antioxdant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were also investigated. The half-maximal inhibitory concentration for DPPH radical scavenging capacity of the pure and 70% ethanol extracts were determined as 0.178 +/- 0.004 and 0.300 +/- 0.005 mg/mL, respectively. Total phenolic contents of the pure and 70% ethanol extracts were determined as 313.2 +/- 5.8 and 278.0 +/- 2.9 mg gallic acid equivalents/g extract, respectively. The total flavonoid contents of the pure and 70% ethanol extracts of F. pinicola were determined as 93.8 +/- 1.6 and 100.4 +/- 4.5 mg quercetin equivalents/g extract, respectively. Both the pure and 70% ethanol extracts (1-10 mg/ml) were investigated for their activities on GPx, SOD, and CAT enzymes in vitro; maximum concentrations of both F. pinicola extracts effectively activated the GPx and SOD enzymes at around 20-35% and the CAT enzyme at 2-12%. Gallic acid is one the main ingredients of F. pinicola extract; therefore, the gallic acid content of the extract was determined by high-performance liquid chromatography, and its corresponding modulatory activities on the same enzymes were also investigated in vitro. The results indicate that the beneficial effects of F. pinicola might be related to its high antioxidant potential, its high gallic acid content, and its ability to modify and activate antioxidant enzymes.