The purpose of this study was to determine antioxidant activity and the most abundant phenolics of nine commercial dark beers. In order to estimate the content of both free and bound forms of beer phenolics, the beer samples were subjected to alkaline hydrolysis. The hydrolyzed beer samples exhibited the significantly higher antioxidant activity measured using 2,2'-azino-bis (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays as compared with nonhydrolyzed ones which was associated with the release of free forms of beer phenolics after hydrolysis. The predominant phenolic compounds in analyzed dark beers were hydroxycinnamic acids, especially ferulic and synapic acids, as well as gallic acid belonging to hydroxybenzoic acids. A principal component analysis (PCA) was applied in order to differentiate the investigated dark beers in terms of phenolic compounds and antioxidant activity for both hydrolyzed and nonhydrolyzed beer samples.