ABSTRACT A total of 300 un-sexed Japanese quail chicks (1-wk-old) were randomly allotted to 5 experimental groups to study the effect of citric acid (CA) on performance development, carcass estimates, blood measurements, antioxidant and immune measurements, digestive enzymes, and cecum microbiology traits of growing Japanese quail. The chicks were fed a basal diet supplemented with CA (5, 10, 15, and 20 g/kg in diet) had significantly (P < 0.05) greater live body weights at 3 and 5 wk of age and increased weight gain across all experimental periods (1−3, 3−5 and 1−5 wks of age) compared to the control group. No significant difference was found in any of the measured carcass traits. The digestion coefficients of crude protein, ether extract, crude fiber, and nitrogen free extract as well as metabolizable energy significantly improved (P < 0.05) in all treatment groups compared to the control. CA supplementation from 10 to 20 g/kg had increased digestive enzyme activities (amylase and lipase). All treatment groups had higher (P < 0.05) albumin and globulin concentrations than the control group. A significant (P < 0.05) decrease in phosphorus (P) concentrations in the plasma was observed in all treatment groups. The IgG levels were greater (P < 0.05) in the 5 or 10 g/kg groups than the control group. Chicks fed CA at different levels had significantly decreased caecal content of TBC, coliform, E. coli, and Salmonella. We concluded that the inclusion of CA (especially 10 g/kg diet) in growing Japanese quail diets improved growth performance, immune response, and health.