The phenolic composition and antioxidant potential were determined in grape berries, berry stem, leaves, leaf petiole and shoots of commercially popular variety Kishmish Chornyi (Sharad Seedless) at various stages of maturation. The berries and berry stems at the initial stage of maturation showed high amounts of total phenolics, flavonoids, flavonols, flavan-3-ols and antioxidant activity in terms of ferric reducing antioxidant power (FRAP). The effect of maturation was profound in grapes with a drastic reduction in various phenolic components and the FRAP value. The berries obtained at the last two harvests showed high anthocyanins and reducing sugars, but the least amount of all phenolic components and thus the antioxidant activity; however, berry stems, leaves, petioles and shoots, respectively, showed 7.6-, 2.9-, 2.3- and 1.5-fold higher FRAP values than berries. Thus, besides the berries, different grapevine parts could also become a potential source of phenolics for pharmaceuticals or functional foods.