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 from 1-42 days of age. A total number of 156 unsexed one-day-old Japanese quails were used and randomly distributed to three equal groups; each group was distributed into four replicates of 13 quails. The 1st group (C) was fed the basal diet with antibiotic (Amoxicillin) 1g/kg diet, while the 2nd (T1) and the 3rd (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 compared with T2 and control groups. The birds in T1 group had significantly (P<0.05) lower mortality rate during the periods of (4-6) and (0-6) weeks of age as compared to other groups. Carcass, liver, gizzard and giblets% 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.