This work was designed to study the effects of stocking density (SD) without or with yeast extract (YE) supplementation on carcass traits and some blood biochemical parameters of growing Japanese quail. A total number of 340, 7-days old unsexed 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 (4 replicates/group) in a complete randomized design. The 1st group was reared in normal density (ND; 10 birds/replicate) and fed the basal diet without any supplementation; the 2nd, 3rd, 4th, 5th and 6th groups were reared in high density (HD; 15 birds/replicate) and fed the basal diet supplemented with 0, 1, 2, 3 and 4 mg YE / kg diet, respectively. The treatment with 1 mg YE / kg diet of groups stocked at HD resulted significantly increased in the relative weight of liver, gizzard and giblets comparable with either HD or untreated group kept at HD. Total protein and albumin values were significantly increased by dietary YE supplementation of HD groups compared with ND and HD without dietary YE supplementation. It is worth to note that, quail chicks groups housed at ND have increase A/G % compared with the groups housed at HD with or without YE supplementation. Increasing SD without or with dietary YE supplementation at different levels had significantly (p < .0001) increased plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) concentrations compared with the chicks stocked in ND. However, there were no significant differences were observed among all experimental groups due to increasing density without or with dietary YE supplementation on kidney functions (plasma creatinine and urea levels). From the obtained results it could be concluded that dietary supplementation of YE can positively attenuate the stress applied upon growing quail reared under HD through enhancing some carcass traits, liver and kidney functions.