Astaxanthin extracted from shrimp ( Litopenaeus setiferus) byproducts using flaxseed oil (FO) was evaluated for the kinetics of lipid oxidation of FO containing astaxanthin (FOA) and astaxanthin degradation. The FOA was analysed for astaxanthin content, free fatty acids (FFA), peroxide value (PV), fatty acid methyl ester profiles (FA), and colour. The amount of extractable astaxanthin in the shrimp byproducts was 4.83 mg 100 g −1 of shrimp waste. FOA and FO had similar alpha-linolenic (ALA) content. The FO was lighter and more yellow in colour than FOA. The oxidation rate of FOA was lower than that of FO. When FO and FOA were heated to 30 °C, both oils exhibited minimal lipid oxidation with increasing heating time, whereas FO, when heated to 40, 50 and 60 °C, had a higher lipid oxidation rate than FOA with increasing heating time from 0 to 4 h. Astaxanthin was an effective antioxidant agent in FO when it was heated from 40 to 60 °C. The degradation of astaxanthin in FOA could be described by first order reaction kinetics. Astaxanthin was stable in FO at 30 and 40 °C, while significant increases in degradation were observed at 50 °C and 60 °C. The rate of astaxanthin degradation in FOA was significantly influenced by temperature.