This study was investigated to determine the effects of two separate sources of fat (sunflower oil, tallow) on growth efficiency and carcass characteristics of broiler chicks reared at age 42 days. using 160 (Ross 308) broiler chicks of one day old. Chicks were distributed fully randomized to 4 treatments based on a system with 4 replicates of 10 chicks. The dietary treatments consisted of: T1, diet containing 5% tallow until the end of the experiment, T2 diet containing 5% sunflower oil until the end of the experiment, T3 diet containing 5% tallow for 21 days of age (grower period ) then sunflower oil till 42 days of age (finisher period ), T4 diet containing 5% sunflower for 21 days of age then 5% tallow until 42 days of age. The performance parameter measured in 21 and 42 days the carcass parameters were measured in the end of the study. The results show that T2 use 5% sunflower oil until the end of the experiment in grower period, weight gain and feed conversion ratio were significantly (p>0.05) improved compared to those nursed by other diets therapies. However, the results in finisher period in T1 there was significant effect (p>0.05) in intake of feed compare to the other treatments. As well as the results of accumulative values of these three traits, a significant (p>0.05) increase in accumulative body weight and weight gain in T3 and were significantly (p>0.05) improved the conversion ratio in T2 and T3 compared to other treatments. The results of carcass traits there were significant effected (p>0.05) in dressing percentage in T1 and T2 compared to other treatments but there were no significantly affect in carcass weight, gizzard and abdominal fat percentage.