Fish-oil supplementation can reduce circulating triacylglycerol (TG) levels and cardiovascular risk. This study aimed to assess independent associations between changes in platelet eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and fasting and postprandial (PP) lipoprotein concentrations and LDL oxidation status, following fish-oil intervention. Fifty-five mildly hypertriacylglycerolaemic (TG 1.5-4.0 mmol/l) men completed a double-blind placebo controlled cross over study, where individuals consumed 6 g fish oil (3 g EPA+DHA) or 6 g olive oil (placebo)/d for two 6-week intervention periods, with a 12-week wash-out period in between. Fish-oil intervention resulted in a significant increase in the platelet phospholipid EPA (+491 %, P<0.001) and DHA (+44 %, P<0.001) content and a significant decrease in the arachidonic acid (-10 %, P<0.001) and gamma-linolenic acid (-24 %, P<0.001) levels. A 30 % increase in ex vivo LDL oxidation (P<0.001) was observed. In addition, fish oil resulted in a significant decrease in fasting and PP TG levels (P<0.001), PP non-esterified fatty acid (NEFA) levels, and in the percentage LDL as LDL-3 (P=0.040), and an increase in LDL-cholesterol (P=0.027). In multivariate analysis, changes in platelet phospholipid DHA emerged as being independently associated with the rise in LDL-cholesterol, accounting for 16 % of the variability in this outcome measure (P=0.030). In contrast, increases in platelet EPA were independently associated with the reductions in fasting (P=0.046) and PP TG (P=0.023), and PP NEFA (P=0.015), explaining 15-20 % and 25 % of the variability in response respectively. Increases in platelet EPA+DHA were independently and positively associated with the increase in LDL oxidation (P=0.011). EPA and DHA may have differential effects on plasma lipids in mildly hypertriacylglycerolaemic men.