This work was conducted to investigate dietary supplementation of oyster mushroom fruiting bodies on biochemical and histological changes in hyper and normocholesterolemic rats. Six-week old female Sprague-Dawley albino rats were divided into three groups of 10 rats each. Feeding a diet containing a 5% powder of Pleurotus ostreatus fruiting bodies to hypercholesterolemic rats reduced plasma total cholesterol, triglyceride, low-density lipoprotein (LDL), total lipid, phospholipids, and LDL/high-density lipoprotein ratio by 30.18, 52.75, 59.62, 34.15, 23.89, and 50%, respectively. Feeding oyster mushrooms also significantly reduced body weight in hypercholesterolemic rats. However, it had no adverse effects on plasma albumin, total bilirubin, direct bilirubin, creatinin, blood urea nitrogen, uric acid, glucose, total protein, calcium, sodium, potassium, chloride, inorganic phosphate, magnesium, or enzyme profiles. Feeding mushroom increased total lipid and cholesterol excretion in feces. The plasma lipoprotein fraction, separated by agarose gel electrophoresis, indicated that P. ostreatus significantly reduced plasma ${eta}$ and pre-${eta}$-lipoprotein but increased ${alpha}$-lipoprotein. A histological study of hepatic cells by conventional hematoxylin-eosin and oil red O staining revealed normal findings for mushroom-fed hypercholesterolemic rats. These results suggest that a 5% P. ostreatus diet supplement provided health benefits by acting on the atherogenic lipid profile in hypercholesterolemic rats.