ABSTRACT A 2×3×2 factorial design experiment was performed including two sources of fiber (corn cobs and wheat straw), three levels of fiber (3, 6 and 9 %) and two levels of enzyme (without or 250 g/kg diet) through the experimental period (1-5 weeks of age). A total number of 360 unsexed one week old Cobb broiler chicks were randomly distributed into 12 treatment groups of 30 chicks each with 3 replicates (10 chicks each). Growth performance (live body weight, body weight gain, feed intake and feed conversion ratio) were studied through out the period from 1- 5 weeks of age. Results obtained indicated, significant (P<0.01) improvement in most traits of growth performance (live body weight, body weight gain and feed conversion ratio) in groups fed corn cobs diet through all the periods studied comparatively with those received wheat straw diets, except, feed intake, in which increased (P<0.01) in groups fed wheat straw diets. However, significant (P<0.01) improvement in all traits of growth performance was observed for chicks fed diets containing 3% crude fiber level when compared with those fed diets containing 6 or 9% crude fiber levels. Addition of enzyme to the diets of broiler chicks significantly (P<0.01) improved live body weight, body weight gain and feed conversion ratio, while feed intake was decreased due to through out the experimental periods studied enzyme supplementation on broiler chicks diet. Chicks fed corn cobs diet at 3% crude fiber level with enzyme supplementation recorded the highest values of growth performance of broiler chicks while the lowest values were obtained by chicks fed wheat straw diets at 9% crude fiber level and without enzyme supplementation. It could be concluded that, supplementation of enzyme to diet contained corn cobs at 3% crude fiber would be suitable of broiler chicks through 1- 5 weeks of age for obtaining high growth performance. Key words: Growth performance, corn cobs, wheat straw, enzyme, crude fiber.