Antioxidant and genotoxic properties of hispidin isolated from the Phaeolus schweinitzii mushroom were evaluated with various assays. Hispidin demonstrated strong free radical scavenging, oxygen radical absorbance capacity, and ferric-reducing antioxidant power; in all applied assays, hispidin exhibited antioxidant capacity similar to or higher than that of the reference antioxidant Trolox. Genotoxic activity of hispidin was assessed using different end points: chromosome aberrations, micronuclei, sister chromatid exchanges, and primary DNA damage (detected by the comet assay) in human lymphocytes in vitro, and gene mutations in the Salmonella/microsome test. Hispidin did not increase the frequency of chromosome aberrations, micronuclei, or primary DNA damage in human lymphocytes in vitro and did not produce reverse mutation in bacterial cells. However, we identified in human lymphocytes a statistically significant dose-dependent increase in sister chromatid exchange frequency and a decrease in replication index and nuclear division index values.