Breast cancer is the second main cause of death among women. The use of medicinal plants has been common in many countries since ancient times. The aim of this study was to evaluate the antioxidant and anti-proliferative potential of Achillea millefolium L. The antioxidant activity of the aqueous and hydroalcoholic extracts of Achillea millefolium L. leaf and flower was measured by DPPH and FRAP method while its anti-proliferative activity on MCF-7 human breast cancer cell line was evaluated using MTT assay.  The ethanolic extract of the leaf and the methanolic extract of the flower had the highest radical scavenging and ferric ion reducing activities. Time and dose-dependent cytotoxic effects of different extracts were observed on MCF-7 cells. The difference in cell viability between hydroalcholic (methanol and ethanol) and aqueous extracts of leaf and flower was significant (P< 0.05), but there was no significant difference in cell viability between methanolic and ethanolic extracts of leaf (P< 0.05). IC₅₀ values varied between 7 and 93 μg/ ml with ethanolic extracts being more cytotoxic and flower extract exhibiting a higher antiproliferative effect than leaf extract. The presence of antioxidant activity as well as high cytotoxic effect of all examined extracts suggest that Achillea millefolium may possess a potential chemotherapeutic activity for breast cancer treatment.