Fish is a well-known source of proteins, minerals, fat-soluble vitamins, antioxidants and other bio-active ingredients. Fish and its processing by-products are relatively cheap raw materials however still rarely are used to create food products with increased nutritive value, functional foods or feed supplements. Application of certain strains of probiotic bifidobacteria for fermentation of non-dairy substrates is a great challenge for industry-targeted research and industry with further offering to the market of functional food products. Our study is the first report on application of bifidobacteria for fermentation of fish. It was shown that a new fish-based functional food product can be obtained after fermentation of Baltic herring mince, supplemented with carbohydrates and NaCl, with a single-strain probiotic culture Bifidobacterium animalis subsp. lactis Bb12. Evaluation of FT-IR spectroscopy data indicated changes of proteins and the composition of total carbohydrates in fermented Baltic herring samples compared to the control. Glucose and sucrose ensured quick acidification and the decrease of pH, to achieve the cell count of B. lactis Bb12 up to 10 8 CFU gG 1 , thus meeting requirements of the viable cell-count of probiotic bacteria in functional food products. However the highest cell counts of probiotic bacteria and acidification were reached using fish mince supplemented with sucrose (2%) and NaCl (1%). The obtained fermented baltic herring paste or its concentrate-after freeze-drying, still with high content of viable probiotic cells (10 7 -10 8 CFU gG 1 ), can be used as functional food product as well as food and feed ingredients.