This study aimed at determining the role of dietary yeast extracts in improving the performance and health of quails reared under high stocking density. A total number of 340, 7-days old unsexed growing Japanese quail chicks with initial body weight of 30.42 g were used in this study. The quails were randomly distributed to 6 experimental groups and 4 replicates maintained per each group in a complete randomized design. The 1st group (40 quails) was stocked at a rate of 10 chicks/replicate (control, ND; 40 quails/m2) and fed the basal diet without any supplementation; the 2nd, 3rd, 4th, 5th and 6th (60 quails/group; stocked at a rate of 15 chicks/replicate; HD; 60 quails/m2) and fed the basal diet supplemented with 0, 1, 2, 3 and 4 mg yeast extract /kg diet, respectively. Addition of yeast extract (YE) at 1 mg/ kg diet to growing quail stocked at HD resulted in a significant (P<0.001) increase in LBW at 6 weeks of age and BWG through 3-5 and 1-5 stages when compared to all treatment groups. No significant differences were observed in feed intake among birds stocked at either ND or HD without dietary YE supplementation. Chicks reared in HD and received basal diet were recorded (P<0.001) the worst FCR values compared with the chicks reared in either ND and HD fed diet supplemented with YE at different levels. Dietary YE supplementation to HD groups resulted in significant enhances in digestive enzyme comparatively with groups kept at ND and HD fed diet without addition of YE. Chicks reared under HD without dietary YE supplementation presented higher values (P <.0001) of serum TC, TG, LDL and VLDL and lower values of serum HDL compared with the chicks reared under ND and HD with dietary YE supplementation at different levels. The values of complement 3 were significantly higher in ND group and HD treated with 1 mg YE / kg diet than the groups housed in HD and untreated and treated with 2, 3 and 4 mg YE / kg diet. HSD fed diets treated with YE at different levels had highest Enterococcus spp. count and lowest total yeast and molds count, E- coli, salmonella spp and coliform. It could be concluded that dietary addition of yeast extract can positively mitigate the stress applied to quail raised under high stoking density by enhancing the antioxidant status, immunological parameters, intestinal pH, cecal microbial counts and as well as feed conversion and intake and growth performance.