The objective of this paper is to study the effects of varying dietary levels ofn-6 : n-3fatty acid ratio on plasma and tissue fatty acid composition in rat. The treatment groups included control rats fed chow diet only, rats fed 50% soybean oil (SBO): 50% cod liver oil (CLO) (1 : 1), 84% SBO: 16% CLO (6 : 1), 96% SBO: 4% CLO (30 : 1). Blood samples were taken at day 15 of pregnancy, and the plasma and tissue were analyzed for fatty acid profile. Then-3PUFA in plasma of Diet 1 : 1 group was significantly higher than the other diet groups, while the totaln-6PUFA in plasma was significantly higher in Diet 30 : 1 group as compared to the control and Diet 1 : 1 groups. The Diet 1 : 1 group showed significantly greater percentages of totaln-3PUFA and docosahexaenoic acid in adipose and liver tissue, and this clearly reflected the contribution ofn-3fatty acids from CLO. The totaln-6PUFA, linoleic acid, and arachidonic acid were significantly difference in Diet 30 : 1 as compared to Diet 1 : 1 and control group. These results demonstrated that the dietary ratio ofn-6 : n-3fatty acid ratio significantly affected plasma and tissue fatty acids profile in pregnant rat.