This study was aimed to investigate the effect of different levels of dietary magnesium on egg shell and internal quality and laying hens performance. Four dietary treatments including a basal diet containing 1.7 g/kg Mg and three additional diets supplemented with 2, 4 or 6 g/kg MgO to provide 2.54, 3.38 or 4.22 g/kg Mg were used in a completely randomised design. A total of 120 white bovans layers (4 treatments, 5 replicates and 6 hen in each repetition) were fed with dietry treatments for 8 weeks. Diets were similar for ME (kcal/kg), CP and other nutrient. Hen-day egg production and egg weight were recorded daily, whereas feed intake, egg mass and feed conversion ratio were recorded biweekly. Four eggs per replicate were randomly collected at the end of each period (each 14 days) to measure egg shell and internal quality. Results indicated increasing concentrations of Mg in the diets significantly increase hen-day egg production and feed intake (P 0.05). No significant diferences were observed on egg weight and egg mass, however this parameters improved numerically by inclusion of Mg in the diets. Different levels of dietary Mg have no significant effect on feed conversion ratio, daily weight gain and shell percentage. Shell weight, shell thickness and eggshell strength increased significantly with addition of Mg in the diets (P 0.05). Dietery treatments significantly increase yolk weight (P 0.05). Mg concentrations have no effect on albumin weight, Haugh unit, yolk shape index and egg shape index. In the total experimental period the addition of Mg to the diets significantly decrease egg yolk color (P 0.05). In conclusion the results of this study indicate that supplementation of Mg up to 4.22 g/kg in the diet of laying hens can improve laying hens performance and increase eggshell quality. Keywords: Laying hens, magnesium, eggshell quality, performance, egg internal quality