Abstract: Background and Objective: The essential oils are vegetal metabolites with a wide range of biological properties and uses. Satureja montana (S. montana) is an aromatic, perennial shrub native in Iran. The objective of present study was to evaluate chemical composition and antioxidant activity of Satureja montana essential oil which is grown in Iran. Methodology: Chemical composition of Satureja montana essential oil was analyzed using gas chromatography-mass spectrometry (GC/MS). The antioxidant activity of Satureja montana was estimated by three methods and compared with TBHQ (TBHQ is a synthetic antioxidant). All calculations were performed using Minitab software and the paired student’s t-test was used to compare the results of samples. Results: The essential oil of Satureja montana contains twenty compounds. The main compound was carvacrol (83.4%) and the results of TBHQ was shown that this plant have a good potential against oxidants. Conclusion: The concentration of carvacrol in Satureja montana essential oil which grown in Iran was higher than other area in the world. So, Satureja montana that grown in Iran could be used for a wide range of food and pharmaceutical industries.