The effects of rosemary extract on protein quality of sea bream fillets cooked with different methods and their changes during frozen storage were investigated. Cooking methods caused a significant decrease in Salt Soluble Protein (SSP) content. During frozen storage, a decrease in SSP content were inhibited by the addition of rosemary extract to sea bream fillets prior to cooking when compared to the controls. An increase in protein carbonyl content after cooking and frozen storage was found to be significant in all cooked samples. The highest formation of protein carbonyl content and the best protection effect of the rosemary extract against protein oxidation were found in fried samples during the frozen storage. Electrophoretic studies showed the dramatic changes in protein bands were observed in only fried samples stored without antioxidant and the rosemary extract inhibited disappearance or a gradual weakening of the protein bands from electrophoretic profiles during frozen storage.