The aim of this study is determining the phenolic acid composition and antioxidant activity potential of Vitis vinifera collected from Osmaniye-Turkey. For determining the phenolic acid composition of the grapes collected in different seasons, samples were screened via a high performance liquid chromatography-diode array detection (HPLC-DAD) instrument. By this way, amounts of gallic acid, 2,3-dihydroxybenzoic acid, vanillic acid, caffeic acid, p-coumaric acid, ferulic acid, cinnamic acid, luteolin and apigenin were determined quantitatively. September sample was the riches one in terms of phenolic acids and flavonoids studied. This is followed by August and October samples, respectively. Total phenolic and flavonoid contents of the samples were also evaluated, using the Folin–Ciocalteu method. October sample was found as the richest one among the samples tested. Antioxidant activities of the samples were evaluated by using four complementary test systems. Results obtained from these samples showed a strong correlation with their phytochemical contents. The most active sample was found as the grape collected in October.