Abstract: Zebrafish (Danio rerio) is a widely used biological model to investigate different chemicals since it has certain similarities with human biology. Present study investigated the impact of monosodium glutamate (MSG); an excessively used food additive in all over the world, on the embryonic development of zebrafish. Acute toxicity experiments were performed for a 4-day period using zebrafish eggs. Ten different test concentrations of Monosodium glutamate (MSG) of 10, 30, 50, 100, 150, 200, 250, 300, 400, 500 mgL⁻1 were used as treatment concentrations. The results clearly indicated that with the increase of the MSG concentrations, different observable deformities are formed in zebrafish embryo. At the low concentrations of MSG such as 10, 30, 50 mgL⁻1 there were no observable malformations in zebrafish embryonic development. However, at high concentrations such as 100, 150, 200, 250, 300, 400, 500 mgL⁻1 there were distinguishable negative alterations such as growth retardation, shrinkage of chorion, yolk sac edema, lack of pigmentation, tail deformities and scoliosis in developing embryos. Zebrafish embryo can be successfully used to investigate excititoxins such as MSG. However, the impacts of these concentrations on internal anatomical and physiological changes in zebrafish embryo should be comprehensively investigated.