The responses of growing turkey to different dietary levels of betaine were investigated during the period from 12 to 20 weeks of age. Therefore, a basal diet was formulated to contain 21.37% CP and 3057 Kcal ME/kg. This diet was supplemented with betaine at levels of 0, 75, 150 and 225 g/100 kg diet. Thus, there were four treatment groups; each was fed to 50 birds (males and females) divided equally into two sub-groups of 25 males and 25 females in each. Results revealed that birds in T3 (150 g betaine/100 kg diet) showed the highest (P≤0.05) final LBW and total weight gain (TWG) as compared to control birds or those in other treatment groups. The superiority in final LBW of birds in T3 was associated with improvement (P≤0.05) in growth measurements including breast width and length of keel, back, shank, tibia and thigh as compared to other groups. Birds in other treatment groups (T2 and T4) did not differ significantly in growth performance parameters from that of the control birds. Males showed better (P≤0.05) growth performance parameters than females. The interaction effect between treatment x sex on all growth performance was not significant. Concentration of total proteins (TP) and albumin (AL) in blood plasma of T3 and T4 groups increased (P≤0.05) as compared to the control ones. Males showed higher (P≤0.05) concentrations of TP, AL and AL: GL ratio than females. Birds in T3 showed the highest (P≤0.05) weights of carcass, giblets, gizzard, liver and heart as well as the highest percentage of giblets. Carcass and gizzard and dressing percentages were not affected by dietary betaine treatments. Males showed higher (P≤0.05) weights of carcass, giblets, gizzard, liver and heart. Females showed the highest (P≤0.05) giblets, gizzard and liver percentages. The interaction effect between treatment x sex on all carcass traits was not significant. Birds in T3 showed the highest economic feed efficiency (EFE %) as compared to other treatment groups. Males showed higher EFE than females. In conclusion, growth performance, blood parameters including protein metabolism, carcass traits and economic efficiency were improved by supplementing diet of grower turkey with 150 g betaine /100 kg diet.