This study was designed to examine the in vitro antioxidant activities of the essential oil and methanol extracts of Satureja macrosiphonia in pre-flowering and flowering stages. GC and GC-MS analyses of the essential oils resulted in the identification of 35 and 24 compounds, representing the 95.1% and 92.6% of the oils, respectively. Major constituents of the oil of the pre-flowering stage were terpinene-4-ol (20.8%) and α-terpineol (14.7%), while in the oil of the flowering stage α-terpineol (26.7%) and borneol (16.6%) were found to be the main components. The samples were subjected to screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene-linoleic acid assay. In general, the polar subfraction of methanol extract in the flowering stage exhibited the greatest antioxidant activity in the DPPH test. In the β-carotene-linoleic acid test, the essential oil of the flowering stage had the highest antioxidant activities.