Hyoscyamus muticus L. subsp. falezlez (Coss.) Maire is an endemic Saharian plant from the Solanaceae family. The aim of this study was to determine the chemical composition and antioxidant activity of essential oil and methanolic extracts of aerial parts of this sub-species. The essential oil of H. muticus L. subsp. falezlez was analyzed by Gas chromatography-Mass spectrometry, while their methanolic extracts of stem, leaf and flower were analyzed by High Performance Liquid Chromatography. The antioxidant activity of the essential oil and methanolic extracts was evaluated using 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays. The oil yield of H. muticus L. subsp. falezlez dried aerial parts was 0.50 % (v/w). Ten compounds, accounting for 87.25 % of the essential oil were identified, among them the oxygenated monoterpenes were the most abundant class (81.07 %) followed by sesquiterpenes which were found in low quantities (1.99 %). Borneol (76.47 %) was the main compound identified, followed by bornyl acetate (4.6 %), 1,3-bis(2-cyclopropyl-2-methylcyclopropyl) but-2-en-1-one (4.19 %) and cedrelanol (1.99 %). The HPLC analysis showed the presence of caffeic, ferulic, trans-cinnamic acids and quercetin in the methanolic extracts of the studied plant. The strongest antioxidant property was obtained by the stem methanolic extract with an IC50 value of 0.541 +/- 0.19 mg/mL while the essential oil exhibited the lowest antioxidant activity (IC50 = 6.26 +/- 0.89 mg/mL). These results demonstrate that aerial parts of H. muticus L. subsp. falezlez are rich in oxygenated monoterpenes with borneol as the main constituent. In addition, we identified ferulic, caffeic, trans-cinnamic acids and quercetin; four phenolic compounds known for their antioxidant properties.