Background: The majority of Achillea species are the most important native economic plants of Anatolia. They include highly bioactive compounds, so they have therapeutic applications. Objective: In the present study, the aim was to investigate in vitro anti-oxidant, cytotoxic and pro-apoptotic effects of Achillea teretifolia Willd extracts (Turkish name: Beyaz civanpercemi). Materials and Methods: The anti-oxidant potential of the extracts was analyzed by the free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and total phenolic content methods. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to detect cytotoxicity of the extracts onhuman prostate cancer cell lines (DU145 and PC-3) and human gingival fibroblast (HGF) cells. mRNA expression levels of pro-apoptotic (bax, caspase-3) and anti-apoptotic (bcl-2) genes were measured by quantitative real-time polymerase chain reaction. Results: The results showed that extracts exhibited a remarkable DPPH scavenging activity, and total phenolic content of the methanol extract was higher than that of the water extract. As time and concentration were increased, the methanol extract exhibited a more powerful cytotoxic effect on prostate cancer cells. In prostate cancer cells, the levels of mRNA expression of the bax and caspase-3 genes were significantly up-regulated (P < 0.05), whereas the expression of bcl-2 was down-regulated (P < 0.05). In HGF cells, there were no cytotoxic effect and apoptosis induction triggered by the extracts. Conclusion: The methanol extract had more powerful anti-oxidant, cytotoxic and pro-apoptotic effects than the water extract. The extracts could be good anti-oxidant sources, and they might include anti-cancer compounds triggering the cytotoxicity and the apoptosis on prostate cancer cells.