This work aimed to investigate the effect of Biofactor (BF) as a water additive antioxidant to avoid the harmful effect of heat stress on productive performance, improving the immunity status and meat quality of Japanese quails. Three hundred and fifty, one-day-old Japanese quails were randomly allotted to  five dietary treatments (each7 replicate with 10 birds/rep). The experimental period lasted for 6 weeks. The first treatment was reared in a separate room with 22-24°C 45-55% RH and used as a negative control (NC). The other treatment groups were reused under heat stress (39°C ± 1; 55-65% RH) for three successive days per week from 11.00 am to 15.00 pm). The second treatment was used as positive control (PC) and supplied with tap water without any supplementation while, the third, fourth, and fifth treatments were reared under the same condition and the other experimental groups were supplied with tap water with additional of 25; 50 and 75 ml BF/liter of water, respectively. The results indicated that Japanese quail exposed to HS significantly decreased of the PC group BW, BWG, FI by 17.1, 19.5 and 10.6 %, and impaired the FCR by 7.22% compared with NC group, at the end of the experiment (6wks.). However, supplementation of 75ml BF significantly increased the BW and BWG by 31.8 and 37.9%, respectively compared with PC group, and complete recovery of the reduction in FI which was statically equal with NC group, also, the FCR was significantly improved by17.02% compared with PC group.  Also, exposure to HS significantly decreased the carcass, abdominal fat, pancreas, and intestinal weight and length of PC by 2.11, 1.72, 12.5, 2.36, and 6.05 %, respectively compared with NC group. On the other hand, the addition of different levels of BF significantly improved carcass  and significantly increased intestinal weight and length compared with that recorded for PC group. Exposure to HS significantly decreased the meat content of CP in HS group from 22.43 to 21.84 by 3.1% compared with NC group, while supplementation 25, 50, and 75 ml/letter of drinking water) the content of CP was increased by 4.72, 12.41 and 14.65 %, respectively compared with the CP content in meat of PC group. Increasing supplementation of BF increased the meat content of EAAs and Non-EAA. Results indicated that PC group exposed to HS had a significant increase in plasma total lipid, total cholesterol, and triglyceride constituents and the total count coliform, anaerobic, and aerobic while the activity of GPx, TAC, LP, AST, and ALP, while, HDL, T3, and T4 were significantly decreased HDL, T3, and T4 activity compared to the other experimental groups. However, increasing supplementation of BF recovery the activity of GPx, TAC, LP, AST, and ALP for the groups under HS and improved all the intestinal microbiota hosts compared to NC and PC groups. Conclusion: Biofactor is a safe product and can used as an anti-heat stress reagent, and oral supplementation of Biofactor by 50 and 75 ml/letter improved the growth performance, biochemical parameters and improved the health of  growingJapanese quail.