Achillea millefolium L., a traditional medicinal plant from the Asteraceae family, is known for its anti-inflammatory, anti-ulcer, and anti-cancer properties, attributed to its rich content of phytochemicals (such as flavonoids, alkaloids, terpenes, tannins, and phenolic acids). This study has focused on the chemical analysis of the oil extracted from the aerial parts of Achillea millefolium subsp. millefolium , cultivated and harvested in Kurdistan, Iraq. The oil was extracted by using a Clevenger apparatus for hydro-distillation and was analysed by using gas chromatography with a flame ionization detector and an HP-5 MS capillary column. The analysis revealed the presence of 1,8-cineole (eucalyptus oil), Artemisia ketone, camphor, linalyl acetate, and D-limonene, with Artemisia ketone having the highest concentration at 15.04% and D-limonene the lowest at 7.51%. The extract of Achillea millefolium has been shown to aid in the treatment of oral mucositis (a common side effect of anticancer chemotherapy), likely due to the flavonoids and tannins present in the plant.