Abstract—Of all the body¡¯s systems, the immune system responds more sensitively to subtle changes in the nutritional status. One nutrient that possesses known and potential effects on health and the immune response is vitamin A. This study investigates the effects of vitamin A administration above dietary requirements on some cells of the immune system in healthy male rats. A 105 male Wister rats were divided equally into three groups (control and two experimental). Test groups were orally administered with vitamin A at two different concentrations (8,000 and 15,000 IU/kg body weight) for 21 days, while the control group was not administered with vitamin A. Blood samples were collected from all rats and assayed for the different cells and antibodies. Compared to their respective controls, total white blood cells and neutrophil counts were significantly increased, while the basophil and total lymphocyte counts were decreased after low dose vitamin A administration. Vitamin A did not affect NK, T, and B lymphocyte cell counts; eosinophils, platelets, and monocytes counts; IgA and IgG concentrations; or hemoglobin and vitamin A concentrations. Therefore, vitamin A affected the immune system in specific ways and these results may be extrapolated to modulate the immune response in humans.