Abstract : The components of essential oils of samples of the aerial parts of Thymus ciliatus (Desf.) Benth., collected at northeastern Algeria in different harvest period, isolated by steam distillation (TC/OL 2015) and hydrodistillation (TC/HE 2016) were analyzed by Gas Chromatography (GC) / Gas Chromatography-Mass Spectrometry (GC-MS and assayed for their antioxidant activities. Although both samples showed similar overall chemical compositions, the principal components were Camphor (44.47-33.18 %), Camphene (7.33-12.22%), Eucalyptol (6.97-6.69%), 4-Terpinenol (3.52- 6.27%), α-Pinene (2.72 -5.84%), β-Myrcene (2.03- 5.30%) and Terpinyl acetate (2.77- 4.57%) in TC/OL 2015 and TC/HE 2016 respectively. A camphor chemotype for T. ciliatus being described for the first time. Antioxidant activity of the obtained oils were examined by the phosphomolybdenum reduction assay and the 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, when compared with those of α-tocopherol and ascorbic acid. The results obtained indicate the existence of an antioxidant activity of the essential oils of the T. ciliatus. Particularly, antioxidant activity of the essential oil of TC/HE 2016 was found to be higher than that of TC/OL 2015.