The aim of this study was to elucidate the effect of dietary fish oil (FO) and a blend of FO and hydrogenated palm oil (PO) on transportation of fatty acids (FA) in plasma lipoproteins of lactating and nonlactating cows. Three lactating and 3 nonlactating Holstein cows (fitted with rumen cannulas) were used in 2 different 3 × 3 Latin square designs that included 3 periods of 21 d. Dietary treatments for lactating cows consisted of a basal diet (Control; no fat supplement), and fat-supplemented diets containing FO (500 g/d/cow) and FOPO (250 FO + 250 PO g/d/cow hydrogenated palm oil). For nonlactating cows dietary treatments consisted of a basal diet (Control; no fat supplement), and fat-supplemented diets containing FO (170 g/d/cow) and FOPO (85 FO + 85 PO g/d/cow). Compared with control and FOPO, FO increased plasma contents of C16:0, C16:1, C17:1, C18:2n6t, C18:2 c9t11 and C20:5n3. Nonlactating cows had higher plasma contents of C18:1t11, C18:1n9c, C20:3n6, C18:2n6c, C23:0 and C22:6n3. Only C18:2n6c was higher in lactating than nonlactating cows (37 vs. 26 g/100g). Compared with control and FOPO, FO increased HDL contents of C18:1t11, C18:2n6t, C18:2 c9t11 and C20:5n3, and increased LDL contents of C18:1t9, C18:1t11 and C20:5n3. Nonlactating cows had higher LDL contents of C18:1t9 and C18:1t11 (1.98 vs. 0.89 g/100g and 2.7 vs. 1.14 g/100g) than lactating cows. In plasma, nonlactating cows had higher contents of total SFA (46 vs. 43 g/100g), MUFA (16 vs. 11 g/100g) and C18:1 tFA (5 vs. 3 g/100g) and lower content of total PUFA (39 vs. 46 g/100g) than lactating cows. Total content of C18:1 tFA was higher in nonlactating cows than in lactating cows (7 vs. 3 g/100g). Overall, results demonstrate clear differences in plasma transport of FA, which depend on dietary FA source and lactation state.