Hyperlipidemia is an important modifiable risk factor of coronary heart diseases. So far, several studies, have indicated the beneficial effects of nuts on plasma lipid profile. Previously, in a pilot study the authors have shown that administration of 20 g/day of Persian walnut (Juglans regia L.) for 8 weeks could decrease plasma triglyceride (TG) concentration by 17% (p value < 0.05). Walnut also increased the plasma HDL-cholesterol level markedly (p value < 0.05). To make the measurements more reliable and to avoid the unwanted walnut side effects (eg, rash, pruritus), this randomized, double blind case-control study was conducted to evaluate the lipid-lowering effect of Persian walnut oil in the population of southern Iran. Sixty hyperlipidemic subjects were randomized into 2 groups; group A patients (n = 29) received walnut oil encapsulated in 500 mg capsules, 3 g/day, for 45 days. Group B patients (n = 31) received placebo and served as the control group. Lipid profiles of both groups were checked before; on days 15, 30, and 45 after the beginning; and 15 days after termination of the study. Plasma TG concentrations decreased by 19% to 33% of baseline in group A patients (p value < 0.05). No statistically significant change was observed in other measured parameters. It was concluded that walnut oil is a good antihypertriglyceridemic natural remedy and should be further explored in more detail.