Ethnobotanical investigation was carried out using questionnaires among majority of El Kala (Algeria) inhabitants. The investigation found that lentisk (Pistacia lentiscus L.) is widely used in traditional therapy, especially in gastrointestinal and dermatological problems.Bioactive phytochemicals were determined by LC-MS/MS, and 14, 13, and 12 compounds were identified in leaves, stems and seeds, respectively. Flavonoids and phenolic acids were the most abundant compounds. Moreover, total phenols (306.5 mg GAE/g), flavonoids (95.25 mg RE/g), and condensed tannins (170.75 mg CE/g) contents were determined in leaves. Also, essential oil composition was investigated using GC/MS and 27 aroma compounds were identified. Monoterpene and sesquiterpene hydrocarbons were the most abundant. Besides, antioxidant activity was performed by DPPH, β-carotene bleaching, and ferrous ions chelating tests; and leaves extracts were more effective (IC 50 of 2.75, 3.45, 13.5 µg/ml), than essential oils (IC 50 of 10.5, 70.5, 157.25 µg/ml), and standards (trolox, 4.75; BHT, 5.25 µg/ml), respectively.