Grape processing and winemaking produce large quantities of valuable by-products, such as grape pomace, stems, and wine lees. All the mentioned by-products have numerous biological properties, among which the antioxidant and antimicrobial activity stand out. Due to the mentioned properties, the by- products have the potential for further use, and their utilization will help to solve the problem of the increasing amount of organic waste generated during the winemaking process. Pomace, the most represented by-product in terms of quantity, is rich in bioactive phytochemicals, especially polyphenols. Very often, however, the wine lees are overlooked, being an equally valuable by-product because they are rich in phenols, vitamins and carbohydrates. In this thesis, the antimicrobial activity of extracts of white, red and rosé wine less against pathogenic bacteria (Escherichia coli, Enterococcus faecalis, Listeria monocytogenes and Staphylococcus aureus) and spoilage bacteria (Pseudomonas aeruginosa and Pseudomonas fragi) was tested. The varieties used are Malvasija dubrovačka and Plavac mali. The analyzes were carried out using three different methods: the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC) and well diffusion method. The results obtained indicate a better antimicrobial activity of the wine less extracts determined by the MIC and MBC methods against spoilage bacteria compared to pathogenic bacteria. The best activity, i.e. the lowest MIC and MBC values (25.5. mg GAE/L) determined by all methods, was shown by a white wine obtained by maceration of grape must in a period of 24 hours before the start of fermentation, against to spoilage bacteria P. aeruginosa and P. fragi compared to the pathogenic bacteria tested.