Seasonal changes in the types of fats and fatty acids were studied in 12 Korean fish species caught off the Tongyeong coast. Triglycerides and free sterols were the main fats found in the fish. The levels of triglycerides increased with higher fat content, while free sterols decreased. Phosphatidylcholine and phosphatidylethanolamine were the main fats in the fish's cell membranes. The most common fatty acids in the fish were 16:0, 22:6 (n-3), 18:1 (n-9), 20:5 (n-3), 16:1 (n-7), and 14:0. As the fat content increased, the levels of monounsaturated fatty acids rose, while polyunsaturated fatty acids decreased. However, the overall polyunsaturated fatty acid content increased with higher fat levels. The level of 16:0 remained stable throughout the seasons.