This experiment was conducted to study the effect of different levels date's by-product (Hafsh, non edible dates produced from date's factories) in the diets with yeast (Saccharomyces cerevisiae) supplementation in water on productive and physiological performance of laying Japanese quail reared at high ambient temperature (40oC and 45oC with 50 % relative humidity). 54 females of 8 weeks-old were weighed and randomly divided into nine different treatments in a 3 x 3 factorial with three replicates arrangement including three date's by-product (Hafsh) levels (0, 10 and 15%) with three levels of yeast (0, 1, 2 g yeast /L) of drinking water. The results obtained that dietary contented with Hafsh or yeast and interactions between yeast level and Hafsh level had a significant effect on all the productive performance ( egg production, egg weight, egg mass/hen/day, feed conversion as (g feed / g egg) ) and improved egg quality in compared with control. Hafsh treatments with or without yeast have significant (p<0.05) difference in some blood biochemical parameters and hormones of quail, i.e., total protein, albumin, total lipids, HDL, progesterone and triiodothyronine hormones were increased , while serum cholesterol and glucose concentrations were decreased significantly (P< 0.05) birds' in compared with control group. The nutrients digestibilities were improved significantly (P< 0.05) by treatment groups. It may be concluded that the application of 2.0g yeast/liter ( in water) with diet contented 10% Hafsh improved the productive performance, egg quality, some physiological parameters, nutrients digestibilities and carcass weight of laying Japanese Quail under high environmental temperature.