The marine environment holds significant importance for life on Earth. Organisms living within it are vital for ecosystems and serve as an inexhaustible source of biologically active compounds. The aim of this research was to investigate the antimicrobial effect of extracted substances from marine organisms collected in the Dubrovnik-Neretva County area. The materials used in the study included soft tissues of marine invertebrates (mollusks such as clams, snails, limpets, sea urchins), and benthic macroalgae (brown, green, and red algae). Active substances were extracted from the samples using two different solvents (ethyl acetate and methanol). The extracts were then tested on bacterial cultures (Salmonella enterica, Staphylococcus aureus, Listeria monocytogenes, Enterobacter aerogenes, and Escherichia coli) obtained from the Public Health Institute of the Dubrovnik-Neretva County. The results demonstrated a significant antimicrobial effect of the extracted substances on bacterial growth. The strongest antimicrobial effect was observed for the extract of the green algae Entermorpha sp. which inhibited the growth of five out of seven bacteria, while the extract of the red algae Corallina officinalis did not show antimicrobial activity against any bacterial strain. These findings provide valuable insights into the potential application of marine organisms as a source of natural antimicrobial compounds. Further research should focus on identifying and characterizing active compounds to understand their mechanisms of action and potentially contribute to the development of new antimicrobial therapeutics.