Aronia berries and grape marc, a by-product of producing wine, are rich in antioxidants. The aim of this work was to study the effects of powders and extracts of aronia berries and grape marc addition on physico-chemical quality indicators, microbiological stability in vitro, and antiradical activity of fondant candies, during storage. In order to obtain the maximum antioxidant activity of the aronia berries and grape marc extracts, the Box-Behnken experimental design was used for optimization of the extraction method using sonication technique. During 35 days of storage, the dry mass fraction of all candies obtained significantly increased, which shows that the fondant candies obtained are stable over time. An important role was played by the antioxidant capacity of the plant materials used, whose chemical composition includes a number of biologically active substances which inhibit the development of microorganisms and allow stabilization of the fondant candies.