Nanoencapsulation is an attractive novel technique used for incorporating essential oils in food preparations and pharmaceutical formulae. This study investigated the effect of nanoencapsulation on the composition of volatile compounds, as well as the antioxidant and anticancer activities of hydrodistilled (HD) Origanum glandulosum Desf. Oil, which was encapsulated into nanocapsules via High Speed Homogenization (HSH) and into nanoemulsions through High Pressure Homogenization (HPH). Thirty-two volatile components were identified using Gas Chromatography-Mass Spectrometry analysis (GC-MS) in HD essential oil representing 99.04% of the total oil content. GC-MS analysis showed that the use of HPH to prepare nanoemulsions negatively affected the active compounds present in HD oil, particularly carvacrol and thymol, whereas the use of HSH led to significant quantitative differences in the composition of volatiles between HD oil and nanocapsules but generated the same profile. Consistent with the differences in total phenolics, total flavonoids, and volatiles identified in HD and nanoparticles, HD essential oil exhibited a higher antioxidant activity (IC 50 4.22 mg/ mL) than nanocapsules (IC 50 57.51 mg/mL) and nanoemulsion (IC 50 78.50 mg/mL), while nanocapsules showed the strongest cytotoxic effect on liver cancer cell line Hep-G2 (54.93 μg/mL) in comparison to HD oil (73.13 μg/mL) and nanoemulsions (131.6 μg/mL).The Origanum genus (Lamiaceae family) includes approximately 38 species that have been studied extensively for potential importance, and uses in flavoring foods and traditional medicine due to their pharmacological characteristics 1 . Origanum species are widely distributed in North Africa, eastern Mediterranean, and Siberian regions. According to Kokkini 2 , Origanum taxa are rich in essential oils that exhibit well-known antioxidant and antimicrobial properties. Based on the chemical composition of essential oils, Origanum species have been classified into three main chemotypes: thymol/carvacrol, linalool/terpinen-4-ol, and sesquiterpenes.Origanum glandulosum Desf., which belong to thymol and /or carvacrol chemotype, is an endemic herb of Algeria, Morocco and Tunisia used in traditional medicine to treat cough, rheumatism, diabetes, and fever 3 . Previous studies have reported antioxidant, antimicrobial, antifungal, and insecticidal activities of the essential oil extracted from O. glandulosum Desf 4-7 . However, to the best of our knowledge, the anticancer properties of this oil have not yet been investigated, despite the focus of several recent studies on the use of natural products with potent antioxidant activity in cancer treatment 8 .Like most essential oils, the use of O. glandulosum Desf. oil in food or pharmaceutical industries may have some limitations owing to its aroma, flavor, volatility, poor dispersibility in hydrophilic media, and sensitivity