Polish fisheries organizations have received the MSC certificate for sustainably catching three species of flat fish in the Baltic Sea. The certificate takes into account 28 indicators and is a requirement for Polish fishermen to reach new markets and increase competitiveness. The process involved a comprehensive expert assessment and stakeholder consultation. The certified flat fish are popular in Poland and Western Europe, and the certificate will allow fishermen to obtain better prices. The article also highlights the health benefits of flat fish, including their content of macro- and microelements and unsaturated fatty acids, which are important for preventing heart disease.