The present experiment was conducted to describe the effects of dietary supplementation of oregano essential oil at different levels, on plasma concentrations of total and HDL cholesterol and triglycerides in broilers. A total 450 Ross 308 male chicks were used in the experiment. There were 3 dietary treatments, each consisting of ten replicates. A replicate was a cage with 15 birds so that each treatment had 150 animals. The control group was fed maise-soybean based diet while the other groups were fed diets supplemented with oregano essential oil at 150 and 300 ppm levels. The experiment lasted for 42 days. Feed and water were provided for ad libitum consumption. At 21 and 42 d of age, blood samples were collected from V. subcutanea ulnaris. Plasma concentrations of total and HDL cholesterol and triglycerides were measured spectrophotometrically by using commercial kits. There was no significant effect on plasma total cholesterol. At 21 and 42 days of age, plasma HDL cholesterol concentrations were significantly lower (P<0.05) in the birds given 300 ppm oregano essential oil when compared with the 150 ppm oregano essential oil group. Plasma triglyceride concentrations were not changed by any dietary treatment.