The present work aims to characterize and quantify the phenolic composition and to evaluate the antioxidant activity of Glycyrrhiza glabra L. (commonly known as licorice) rhizomes and roots. The antioxidant potential of its methanol/water extract could be related to flavones (mainly apigenin derivatives), flavanones (mainly liquiritin derivatives), a methylated isoflavone and a chalcone, identified in the extract. Lipid peroxidation inhibition was the most pronounced antioxidant effect (EC₅₀ = 0.24 ± 0.01 μg mL⁻¹ and 22.74 ± 2.42 μg mL⁻¹ in TBARS and β-carotene/linoleate assays, respectively), followed by free radical scavenging activity (EC₅₀ = 111.54 ± 6.04 μg mL⁻¹) and, finally, reducing power (EC₅₀ = 128.63 ± 0.21 μg mL⁻¹). In this sense, licorice extract could be used as a source of antioxidants for the pharmaceutical, cosmetic and/or food industries.