The first mention of sardine fishing in Croatia dates back to the 13th century, and their processing was soon mentioned as well. The main goal of fresh fish processing is to extend the shelf life while maintaining quality. By lowering the temperature and freezing the fish, unfavorable conditions are created for the life and activity of microorganisms and enzymes. During this research, microbiological testing of fresh and frozen sardine samples revealed that all samples were hygienically correct and that bacterial activity could not affect the further analysis of the sardine. Sardine (Sardina pilchardus) is among the economically most important fish in processing. Sardines that are used in this research were caught in the winter period with an average total fat content of 1.46% ± 0.43%. In order to achieve IQF (individually quick frozen) frozen sardine, a deep-freezing plant is required at a temperature of -35°C to -40°C and a freezing time of 35 minutes for fish fillets and 40 minutes for cleaned fish. When freezing, the fish must be properly frozen so that the cell membranes remain undamaged and retain the cell juices, which enables the fish to retain its taste, juiciness and softness. In the process, it is very important to maintain the best possible quality, that is, as few changes as possible in the composition of fatty acids due to their importance in human nutrition and their positive impact on the prevention of various diseases. The aim of this paper was to compare the composition of fatty acids between sardine samples stored as fresh (0-3°C) and IQF frozen sardine. The purpose of the work was to qualitatively evaluate the composition of fatty acids in IQF frozen sardines in order to determine whether such a processing method is desirable for preserving the quality of food fish products. Research on the fatty acid composition of fresh and IQF frozen sardines revealed different behavior of fatty acid groups. When using fresh and IQF frozen sardines, a decrease in the amount of dry matter and an increase in the amount of water content was observed. During the five-day storage of sardines at 0-3°C, an increase in saturated and monounsaturated fatty acids was recorded, while polyunsaturated and highly unsaturated fatty acids decreased over time. However, with IQF frozen sardines, during 120 days of storage at low temperatures, an increase in all groups of fatty acids was recorded.