The anti-hyperlipidemic effects of dietary supplementation with sea tangle Laminaria japonica were investigated using an animal model in which normal rats were fed either sea tangle, sea tangle ethanol extract (EE-ST) and sea tangle extracted residue (ER-ST). Total lipid and triglyceride levels in the serum were significantly (P < 0.05) reduced in rats fed ER-ST at a dose of 200 mg/kg body weight when compared to hyperlipidemic control rats. Significant decreases in serum total cholesterol and low density lipoprotein-cholesterol levels also occurred in rats fed ER-ST at 200 mg/kg body weight. In addition, the atherosclerosis index and superoxide dismutase in blood lipids were significantly (P < 0.05) lowered in rats fed ER-ST at 200 mg/kg body weight as compared to control rats. In conclusion, sea tangle and ER-ST exhibited beneficial anti-hyperlipidemic and anti-arteriosclerosis effects.