The present study was conducted to examine the antioxidant activities and neuroprotective effects of methanolic extracts from Schizonepeta tenuifolia Briquet (STE). STE ($100;{mu}g/mL$) showed $43.33;{mu}M$ of total phenolic content, 64.43% of radical scavenging activity, and 0.157 of reducing power. In addition, the effect of STE on $H_2O_2$-induced DNA damage in human leucocytes was evaluated by the comet assay, where STE was a dose dependent inhibitor of DNA damage induced by $200{mu}M$ of $H_2O_2$. The protective effect of STE against $H_2O_2$-induced oxidative damage on PC12 cells was investigated by an 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) reduction assay and lactate dehydrogenase (LDH) release assays. After 2 hr of cell exposure to $H_2O_2;(500;{mu}M)$, a marked reduction in cell survival was observed. However, this reduction was significantly prevented by $1-50;{mu}g/mL$ of STE. Therefore, these results suggest that STE could be a new antioxidant candidate against neuronal diseases.