Quercus brantii Lindley (Fagaceae) is a common oak region of South and East Anatolia. For many civilizations, acorns of Quercus species have been considered as food as well as used in folk-medicine. Phenolic composition of the acorns of Q. brantii was studied by high performance liquid chromatography equipped with a diode array detector. To the best of our knowledge, this is the first study regarding a comprehensive separation and identification of the phenolic constituents of Q. brantii acorns. Rapid separation and identification were performed by the reverse phase HPLC-DAD. Identification of the phenolics was also confirmed by UPLC-MS and when necessary structural characterization was accomplished by NMR and FT-IR techniques. As a result, the phenolic composition of the acorns of Q. brantii were realized as gallic acid, methyl gallate, epi-catechin, p-coumaric acid, ellagic acid, rutin and quercetin in the respective elution order of the RP-HPLC chromatogram.