The antioxidant activity, total phenolic content, enzyme inhibition, anticancer properties of Achillea millefolium L. (yarrow), which is generally consumed by humans as herbal tea, were investigated. Yarrow extracts were prepared with different extraction techniques and solvents and the optimum conditions were determined. When the antioxidant activity and total phenolic content results were evaluated, the best yield was obtained with ultrasound-assisted extraction for all solvents. Moreover, the yields from highest to lowest were methanol, water, and acetonitrile. The enzyme inhibition and anticancer of Achillea millefolium L. extracts using methanol were evaluated. The IC50 values for the inhibition of xanthine oxidase and acetylcholinesterase were 4.974 ± 0.54 and 21.891 ± 1.118 µg/mL, respectively. The extract concentration was determined to be 23.85 μg/mL for 50% reduction in growth inhibitory activity cell viability (IC50) against breast cancer (MCF-7).