Two experiments were conducted to determine the influence of dietary concentration of defatted rice bran (DRB) and phytase and fiber-degrading enzyme (FDE) supplementation of DRB-containing diets on performance, characteristics of selected parts of the gastrointestinal tract, and tibia ash of broiler chickens. In Experiment 1, four concentrations of DRB (0, 7.5, 15, and 22.5%) were tested in diets formulated to be isonitrogenous (22% CP) and isocaloric (3,000 kcal MEn/kg). Body weight and feed to gain ratio of broilers from 4 to 35 d of age were not affected by DRB concentration. A decrease in percentage tibia ash (P < 0.08) as dietary DRB increased was indicated. In Experiment 2, diets containing 22.5% DRB were supplemented with phytase (0 and 665 units/kg of diet) and FDE (equivalent to 0 and 1,000 units of xylanase/kg) in a complete factorial arrangement. A corn-soybean meal diet (CS) was included as a fifth treatment. No significant differences among dietary treatments were observed for weight gain and feed efficiency of broilers from 4 to 35 d of age. The MEn values of the DRB diets were greater (P < 0.01) than those of the CS diet, although phytase supplementation of the DRB diet, with or without FDE, reduced (P < 0.01) MEn. Phytase supplementation did not affect percentage tibia ash of chicks fed the DRB diet. The results show that up to 22.5% dietary DRB can be used successfully for broiler chickens when diets are supplemented with available P and fat.