This study investigated the quantitative and qualitative effects of climate and soil properties on essential oil content and composition of Cirsium arvense L. (Asteraceae), which is an important medicinal plant. Root, stem, and leaf tissues were collected from plants found in four regions (Shahrekord, Farsan, Chelgerd and Ardal) of the Chaharmahal and Bakhtiari Province, Iran. GC/MS analysis revealed that the main constituents of essential oils from the various populations were nonadecane, β-citronellol, camphor, heneicosane and phytol. The highest levels of nonadecane (40.1-42%) and camphor (18.1-18.4%) were obtained from roots collected from the Chelgerd region, the most levels of β-citronellol (24.9-25.01%) were obtained from leaves from the Chelgerd region, and the most levels of heneicosane (14.4-15.6%) and phytol (11.8-12.58%) were obtained from stems from the Shahrekord region. The most amount of essential oil (0.34-0.33%) was obtained from roots growing in clay soil in the Chelgerd region. Both climate and soil properties had significant effects on the essential oil of C. arvense. The highestt essential oil contents were obtained from plants growing in clay soil, which seemed to have a greater capacity to hold water and nutrients, both of which promote plant growth and essential oil production.