Plantain (Plantago) species are traditionally used as food products and folkloric medicines in many countries. This study evaluated the antioxidant effects, phytochemical content, and phenolics profile of Plantago lanceolata (ribwort plantain) as an important herb in Turkey. Five different methods were used to measure the antioxidant activity including beta-carotene bleaching, DPPH radical scavenging, reducing power, metal chelating, and phosphomolybdenum total antioxidant assays. Total content of phenolics and flavonoids were also determined. Profiling of phenolic compounds was done using liquid chromatography-electrospray tandem mass spectrometry. Methanolic extracts showed the highest antiradical and reducing activities. Water extracts had strong beta-carotene bleaching (71% at 0.4 mg/mL) and ferrous ion chelating (95% at 0.25 mg/mL) abilities. Methanol extracts had high antioxidant capacity in the phosphomolybdenum assay (145 mg AAE/g extract). Phenolics profiling showed 28 phenolic acids, flavonoid, and phenylethanoid glycoside compounds. A high amount of verbascoside (94.8 mg/g dry aerial parts of plant) was obtained followed by chlorogenic acid, rosmarinic acid, hesperidin, and hyperoside. Plantago lanceolata has considerable potential for use in new food and pharmaceutical products. Also, it could be regarded as a rich source of verbascoside.