The aim of this study was to evaluate the effect of adding Guanidino acetic acidmixture (GAA), Amino Acids (A.A.; Meth. + Lys. + Thr. + Arg.) or both (GAA + A.A.) and b-mannanase (Hemicell HT) to a typical corn soybean meal diets on growth performance, carcass characteristics and economical efficiency of broiler chicks. A total number of 225 day old Hubbard broiler chicks were classified into 5 equal groups, each was subdivided into 3 replicates with 15 chicks. The control group was fed basal (starter, grower and finisher) diets without supplementation, while the other groups (T₁), (T₂), (T₃) and (T₄) were fed the basal diets supplemented with 600mg G.A.A/kg.; 1450 mg A.A. kg. diet or both (600mg GAA + 1450 mg A.A.) and300mg b-mannanase/kg diet, respectively. Diets and water were provided I. throughout the experimental period (1-35) days of age. The results indicated that: Live body weight, daily weight gain and daily feed intake for the broiler chicks fed basal diets supplemented with GAA + A.A., (T₃) or b-mannanase, (T₄)reflected the highest significant results than those fed control basal diets at 1-35 days of age. Chicks fed T₁, T₂ and T₃ diets had significant better FCR compared with those fed control or T₄ diets. The best protein (PCR), energy (ECR) conversion ratio and the highest performance index (PI) and production efficiency factor (PEF) were recorded for the group supplied with GAA + A.A., (T₃) compared with other dietary treatments. The group of chicks fed AA mixture recorded significantly higher percentages of dressing and ready to look comparing to control group. While, the same group (T₂) showed lower value of giblets % as comparing to unsupplemented treatment. Economical evaluation, the chicks fed basal diets supplemented with different feed additives (T_1-4) supported the calculated economic efficiency percentages compared to control group and the corresponding increasing values were 15.73, 1.35, 35.89 and 14.14% respectively.