The aim of this study was to investigate the synergism of protein sources (plant or animal) and enzymes in diet on broiler performance, gastric enzymes activity, some blood parameters and histological observations. A total number of 270 one day unsexed Hubbard chicks were distributed into 6 equal groups. Each group has 3 replicates of 15 birds each. The first group served with plant source protein, the second one served with animal source protein, the rest 4 groups were supplemented with 100 or 200mg commercial enzymes per kg diet (plant or animal source of protein). Our results indicated that the benefits of the use of 100mg enzyme per Kg plant source of protein in diets on broiler performance, economic efficiency and increase in gastric enzymes activities (when comparing with the rest of groups) which explain the improvements in the FCR. The current trial indicated also, that broiler diets supplemented with enzymes increased significantly the total proteins and globulin levels and reducing the cholesterol level in serum, which might supported by the enhancement of some immune organs (spleen and bursa).