The phenolic profile of barley ( Hordeum vulgare L.) leaves, seeds, awns, and stems, collected in two different locations from Portugal, was determined by a high-performance liquid chromatography/diode array detector (HPLC/DAD). A total of 28 compounds were identified and quantified, which included 4 phenolic acids, 6 C-glycosylflavones, and 18 O-glycosyl-C-glycosyl flavones, with some of them acylated. Distinct profiles were noticed among the analyzed materials. The greatest diversity of compounds was found in barley leaves (26 flavonoids and 2 phenolic acid derivatives), which also exhibited the highest concentration of phenolics. Isoorientin-7-O-glucoside (lutonarin) was the major compound in leaves, while, in general, the pair isovitexin-7-O-rutinoside plus isoscoparin-7-O-glucoside were the main phenolics in the other materials. Thus, barley leaves may constitute an important dietary source of protective compounds, which could be used, for example, to take profit from the wastes resulting from alcoholic drink obtainment.