The aim of this study was to determine the effects of grit supplementation to the diets containing maize and barley as cereal grains on performance and slaughter characteristics in broilers. In the experiment, a total of 160 Ross 308 male broiler chicks were allocated to 2 experimental groups with 4 replicate pens containing 20 birds per each for 5 weeks of experimental period. Granite grit was added at the level of 0 and 0.8% to the basal diets containing barley and maize as cereal grains for control and treatment groups, respectively. Granite grit supplementation had no significant effect on final body weight and body weight gain. Feed intake during the experiment was significantly reduced by grit supplementation (P<0.05). However, no significant differences were observed with the feed conversion ratio. Granite grit supplementation to the diets of broilers increased the relative weight of gizzard (P=0.001) and decreased the relative weight of abdominal fat (P <0.05). Dietary treatments did not affect blood serum total cholesterol and triglyceride. In conclusion, granite grit supplementation might be used in broiler nutrition due to having increment in the relative weight of gizzard and reduction in relative weight of abdominal fat.