A total number of 240 unsexed, one-day old Arbor Acres broiler chicks were randomly distributed into 6 experimental groups of 40 birds each. Each group contained four replicates of 10 birds each. A factorial design (2×3) was used, two diet densities (control and 10% low) and three enzyme sources (control, bacterial phytase and fungal phytase), Live body weight and feed consumption were recorded and body weight gain and feed conversion were calculated during starting, growing and whole experimental periods. At 6 weeks of age, three birds were randomly taken from each treatment and slaughtered to measure carcass traits. The results revealed that, body weight at 3rd and 6th week and body weight gain during the period from 0-3 and 0-6 weeks of age for birds fed control diet were significantly higher (P≤0.05) than birds fed low density diet. However, feed consumption was not significantly affected by diet density, while feed conversion ratio of birds fed control diet was significantly better (P≤0.05) than birds fed low density diet especially during the starting period from (0-3 weeks). 
Body weight and body weight gain of broiler chicks were not significantly affected by phytase sources. Feed consumption of chicks fed diet supplemented with fungal phytase at 3-6 and 0-6 weeks of age was significantly (P≤0.05) higher than the other treatments. However, feed conversion ratio at 3-6 weeks of age for birds fed diet supplemented with fungal phytase was not significantly improved. The birds fed control diet had significantly higher pre-slaughter weight, carcass weight and giblets percentage than the birds fed low density diet. The birds fed diet supplemented with fungal phytase had significantly (P≤0.05) higher pre-slaughter weight and lower giblets percentage than the birds received bacterial phytase.