This experiment was designed to evaluate the effects of synbiotic and garlic powder as alternatives to antibiotic on growth performance and carcass criteria of Japanese quails until 42 days of age. In a complete randomized block experimental design, a total number of 156 unsexed one-day-old Japanese quails were allocated randomly distributed into three equal groups; treatment group consisted of four replicates of 13 each. All birds were kept under the same managerial conditions. The first group (C) was fed the basal diet with antibiotic (Amoxicillin) 1g/kg diet and served as control, while the second (T1) and the third (T2) groups were fed the basal diets supplemented with synbiotic (PoultryStar^® sol) and garlic powder (Allium sativum) at the level of 1g and 20g/kg diet, respectively. The results indicated that birds fed diet supplemented with 1g synbiotic/kg diet had significant (P≤0.05) higher body weight, daily body weight gain, feed consumption and feed conversion ratio as compared with T2 and C groups. Group T1 had no mortalities. Carcass, liver, gizzard and giblets percentages were significantly (P<0.05) higher in T1 group compared with other groups, while, the highest value (P≤0.05) of abdominal fat% was obtained in control one. From these results, it could be concluded that the supplementation of 0.1% synbiotic as an alternative to antibiotic in Japanese quails diets were highly recommended to obtain higher growth performance and carcass criteria.