Fish are rich in high-quality protein. Additionally, they are known for their high content of polyunsaturated fatty acids such as EPA and DHA. This review aims to provide an overview of the lipid fraction of selected fish species, exploring methods of manipulating fatty acid content and discovering the resulting health benefits for dogs and cats. The article discusses innovative methods used to manipulate fatty acid content in fish, including nutritional strategies, selective breeding and new technologies. Based on the current scientific literature, the article synthesizes knowledge on the impact of these manipulation methods on the nutritional quality of fish. Additionally, literature data were presented indicating the positive aspects of including fish in the diet of dogs and cats. EPA and DHA are responsible for a number of health benefits, including supporting the circulatory system, cognitive functions and the learning process, an element of diet therapy in the treatment of cancer, and alleviating pain associated with degenerative joint diseases.