The objective of the research was to assess the quantity and quality of protein and amino acids contained in fish from the Vistula Lagoon. The research covered the fish species (eel, herring, bream, pikeperch, roach, and perch) most frequently caught in this water basin. The basic chemical composition of fish meat (content of protein, lipids, and water) was determined as were the digestibility of protein and the composition of amino acids. The fish examined were lean and medium-fat (except for eel) and contained 14.4 to 19.5 g/100 g of highly digestible proteins (98.3 – 98.8 %). The protein of the fish tested, especially that of pikeperch, contained high amounts of exogenous amino acids. In 100 g of meat, there was 5.79 to 8.85 g of those elements appearing essential for organism. The research results show that 100 g of meat of each fish species from the Vistula Lagoon covers with excess the daily protein demand of the adults. The content of exogenous amino acids in the meat of fish from the Vistula Lagoon exceeds their quantity in the standard protein. This proves the high quality of fish protein. The predominant amino acids in the protein are methionine and cysteine, lysine, isoleucine, as well as histidine. Their content ranged from 145.2 to 239.5 % compared to the standard protein.