Abstract: Today, natural colorants are emerging globally due to the fact that are safer and environmentally-friendly. Natural dyes have been employed in dyeing Persian carpet piles for many years. In this study, the dried Achillea was used for dyeing wool yarns. The Iranian wool yarn was scoured, mordanted using some metal salts including Cu, Sn, Al and then dyed with different amounts of dried Achillea powder. Taguchi statistical method was employed to find the effective factors and results of the planned experiments, in order to optimize the dyeing factors. A L9 orthogonal array (four factors in three levels) was employed to evaluate the effects of different parameters in dyeing process. The colorimetric properties of the dyed yarns were evaluated in CIELAB system. Achillea found to have good agronomic potential as a natural dye in Iran. Metal mordants when used in conjunction with Achillea were found to enhance the dyeability and its fastness properties. Therefore this natural dye has good scope in the commercial dyeing of wool yarns used as Persian carpet piles.