Monosodium Glutamate (MSG) is the sodium salt of glutamate (simply glutamate, water and sodium) and is widely used as food additive and as flavoring agent to increase appetite. The present study was to evaluate the effect of daily oral admiration of (MSG) (100mg/kg/day) for 30day on reproductive system of males and females Swiss albino mice. Forty albino mice weighting about (25-30kg) were used in the present study. The animal were divided in two groups: control group (10 males and 10 females)(n=20) and treated group(males and females) n=20.The body weight of the animals detected at the beginning and the end of experiment. At 30 days animals sacrificed and ovaries, uterus, testis were removed and weighted, Samples of ovaries, uterus testis fixed in 10%formaline for histological study. The final result show highly significant increase in the body weight and show significant decrease in the weight of ovaries and testis. The histological study in the treated group of testis show suppression of spermatogenesis, degenerate of seminiferous tubules and congestion of blood vessels. The histological changes in the ovaries such as congested blood vessels of medulla, increased atretic follicles and uterus show necrosis in perimetrium , presence of lacunae in the uterine wall structure . Conclusions: Monosodium glutamate has negative effect on reproductive system for each sex. So that will effect on the fertility .Also the increased body weight could lead to increase the incidence of congestive heart diseases and diabetes mellitus.