Gilthead sea bream ( Sparus aurata ) skin-on fillets, prepared from 48-hour post-harvest iced fish, were individually quick-frozen in an Armfield FT 34-MKII plate freezer, wrapped in a single layer of polyethylene film and stored at -18 °C. Quality changes of the fillets were assessed by sensory evaluation, lipid profile analyses, rancidity development assays and colour measurements of the raw and cooked flesh, over a period of three months. Rancidity development, assessed by measurements of thiobarbituric acid-reactive substances (TBA-RS), proceeded slowly during storage and correlated significantly ( r = 0.955, P < 0.05) with the observed decline in sensory score for cooked fish flavour. Unlike fillet lightness ( L* ), which remained practically unchanged ( P < 0.05) during storage, changes in a* and b* values were quite pronounced, indicating a shift towards reddish/bluish colorations in the cooked flesh. Lipids in fresh Sparus aurata skin-on fillets were composed of triglycerides and phospholipids as major constituents. Small amounts of cholesterol, free fatty acids and diglycerides were noticeable. During frozen storage, both triglyceride (TG) and phospholipid (PhL) contents decreased, while the free fatty acid (FFA), diglycerides (DG), monoglycerides (MG) and lyso-phosphatidylcholine (l-PC) contents increased, particularly with increasing storage time ( P< 0.05). This suggested that TG and PhL were hydrolysed into FFA, DG, MG and l-PC during extended storage. Furthermore, the result at the end of the storage period (3 months) indicated that the decreasing rate of TG was comparatively higher than that of PhL. This was possibly due to the greater activity of lipase in farmed sea bream than phospholipase activity. The major saturated fatty acids (SFA), monoun saturated fatty acids (MUFA) and polyun saturated fatty acids (PUFA) identified in all studied samples, whether raw or frozen, were palmitic (C16:0), oleic (C18:1 ω -9) and linoleic (C18:2 ω -6) acids, respectively. Frozen storage significantly affected the fatty acid composition of Sparus aurata fillets. Since triglycerides and phospholipids underwent hydrolysis into FFA during storage, free PUFA and MUFA could have undergone oxidation, which is supported by the increasing TBA values. This result was evidenced by the significant decrease in PUFA and MUFA during storage. As SFA increase and PUFA decrease synchronously following frozen storage of fish fillets, PUFA/SFA ratio decreased (P<0.05) compared to raw samples. Marked decreases in ω-3 PUFA, especially eicosapentaenoic acid (EPA; C20:5 ω-3) and docosahexaenoic acid (DHA; C22:6 ω-3) were observed as the frozen storage time