Backgrond: Thymus daenensis Celak. subsp. daenensis is one of the endogenous Thymus species in Iran. The plant is traditionally used as carminative, digestive, antispasmodic, antitussive and expectorant in Iran. Objective: To study the Composition of the Volatile Oil of Thymus daenensis Celak. subsp. Daenensis. Method: In this study, the hydrodistilled oil of the aerial parts of T. daenensis subsp. daenensis was analyzed using GC/FID and GC/MS. The result indicates that the oil contains over twenty-six components (99.7%). The main components were thymol (74.7%), p-cymene (6.5%), β-caryophyllene (3.8%) and methyl carvacrol (3.6%). Conclusion: This species has rich in phenolic substances specially thymol which might considered as a substitute for Thymus vulgaris.