The aim of the research was to determine the effects of red ginseng root powder on performance, immune system, caecal microbial population and some blood parameters in broilers. A total of 224 daily Ross 308 male broiler chicks were divided into one control group and three experimental groups each containing 56 chicks. Red ginseng root powder was added to the diets of groups at the level of 0, 75, 150 and 225 mg/kg, respectively. The experimental period was 38 days. There were no differences in growth performance. Addition of 225 mg/kg of the red ginseng root powder increased the relative weight percentages of spleen and gizzard (P<0.05). Ginseng root powder supplementation didn’t affect biochemical parameters and antibody titers in blood serum. The values of haemoglobin, leukocytes, red blood cell distribution width and mean corpuscular haemoglobin concentration in group fed diet supplemented with 225 mg/kg ginseng were increased significantly (P<0.001). The count of Lactobacillus spp. in the caecum (P<0.05) was increased with 75 mg/kg ginseng root powder addition. As a result, improvements were provided in immune organ weight and some hematological parameters with the addition of 225 mg/kg and in Lactobacillus spp. count in caecum with the addition of 75 mg/kg red ginseng root powder to the diets in broilers. Further studies are required to evaluate the bioavailability of the active compounds of red ginseng root powder and to determine the effects of its various doses on performance, immunity, antioxidant potential and intestinal microflora under various stress conditions in poultry.