In this study the effect of various processing techniques on the fatty acid composition of mussel, a member of bivalves, was investigated. According to the results, applied techniques such as smoking, pickling, and different kinds of cooking are recorded to have caused important changes in their fatty acid compositions. It was also seen that these changes were occurred from PUFA's, ecosapentaenoic (EPA) (C20:5 n-3), and docosahexanoic (DHA) (C22:6 n-3) which are important especially in nutrition. Generally, in accord with the processing technique, a decrease in different proportions was found in the quantity of ecosapentaenoic and docosahexanoic acids. Maximum decrease in the mentioned fatty acids was especially observed in the mussels processed by frying and cooking.