The objective of this experiment was to evaluate the effects of different levels of unprocessed rice bran with and without enzyme on performance and size of the digestive organs of broiler chickens. A total of 416 1-day-old male broiler chicks (Avian Farm) were randomly distributed into 8 treatment groups, each with 4 replicate groups containing 13 chicks. Rice bran with and without enzyme supplementation was used at 0, 10, 15 and 20% in the diets of broiler chicks. The inclusion of rice bran into the broiler diets significantly decreased body weights and body weight gains. Feed intake was significantly reduced by the increased level of rice bran in the broiler diets at the 21(st) day of the experiment. However, at the 42(nd) day of the experiment, broilers fed the 20% rice bran diet consumed significantly more feed than other groups. Feed conversion ratios were significantly altered as the level of rice bran increased. Also, the increasing levels of rice bran in broiler diets decreased hot carcass weights significantly. Hot carcass yield was significantly (P<0.05) less in broiler chickens given diet containing 20% of rice bran as compared to the other diets. In general, there was an increase in relative size of the digestive organs when rice bran was included in the diet. There were no significant effects of enzyme supplementation and interaction between diet and enzyme supplementation on performance and size of the digestive organs of broiler chickens.