ABSTRACT The impacts of cooking on biochemical, fatty acid composition, and lipid nutritional quality index of the red‐mouthed rock shell Stramonita haemastoma collected from the Channel of Bizerte were examined for the first time. Results showed that the boiling process induced an oxidation of protein as expressed by a significant decrease in protein content as well as an increase in advanced oxidation protein products (AOPPs) synthesis in cooked snails. Moreover, the increase of malondialdehyde (MDA) level in cooked snails indicates the occurrence of lipid peroxidation. Regarding the composition of fatty acids, cooking was found to significantly enhance the amounts of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA). However, the amounts of polyunsaturated fatty acids (PUFA) in cooked snails dropped considerably. This decrease is caused by a notable drop in the proportions of arachidonic (ARA), eicosapentaenoic (EPA), docosahexaenoic (DHA), and linolenic acids (LA). Despite this, the values of lipid nutritional quality indices indicated that the nutritional value of the product is still acceptable as they are comparable to those recommended by the Food and Agriculture Organization (FAO) and World Health Organization (WHO). Since S. haemastoma is abundant year‐round, it also has a wide geographic distribution and a high nutritional value as proved by results from this study; it can thus be included in the Mediterranean food composition table.