The current research was conducted to study the effect of dietary supplemental of glycine (gly) levels 0.1 and 0.2 % on modulating productive performance in Mandarah (M) during laying period from 28 to 40 weeks (wks.) of age. The 1st treatment (T1) was fed the basic diet and served as the control treatment with no additional gly. The 2nd and 3rd treatments were fed the basic diet supplemented with 0.1 and 0.2 % gly/kg diet, respectively. Results indicated that hens fed (T2} and (T3) supplementation significantly improved feed conversion ratio for all intervals except from (28 to 30 wks. of age) compared to control. Egg number, egg weight and egg mass values were significantly increase in M hens fed diets containing T2 or T3 compared to control T1 during the whole period studied. Egg quality {shell (thickness and %), albumen %, yolk (% and index)} were significantly affected due to T2 and T3 supplementation to hens. Significant increases have been recorded in abdominal fat % and triglyceride (TG) values of hens in T2 and T3 compared to T1 (control) values at 40 (wks.) of age. Significant decreases have been recorded in litter traits (pH, moisture, nitrogen and ammonia %) of hens of T2 compared to control (T1) values at 40 wks. of age. The results of the current research indicated that gly supplementation during the laying period promoted the productive performance and had beneficial effects on quality of poultry litter.