The fatty acid (FA) composition was determined in the mussel (Mytilus galloprovincialis Lamarck 1819) cultured at the longline system located in Sinop (Black Sea) from October to September. Seasonal variation of lipid was significantly different throughout the study period; the highest value was in winter (1.90±0.10% wet weight) and the lowest value in spring (1.45±0.22%) (p<0.05). The polyunsaturated fatty acids (PUFAs) were dominant lipids in spring and winter including 55.80% and 55.63% of total lipids, respectively, while PUFAs in the summer and autumn were considerably higher than values in spring and winter, comprising 52.97% and 50.67% of total lipids, respectively. The palmitic acid (PA, 16:0) saturated fatty acids (SFAs), 11-eicosenoic acid (EA, 20:1n-9) mono-unsaturated fatty acids (MUFAs), and docosahexaenoic acid (DHA, C22:6 n-3) PUFAs were the most dominant fatty acids of all. The results showed that all fatty acids were the PUFAs with the highest percentage. Within this group, the eicosapentaenoic acid (EPA, C20:5 n-3) and DHA fatty acids presented the highest levels. Also, the lowest and the highest n-3/n-6 ratio were in autumn (1.44%) and winter (2.23%), respectively. These results suggest that spring was the more suitable period for collecting mussels and for healthy diet of humans.