This study was conducted to investigate the effect of different levels of yeast supplementation to laying hen diet on egg production, egg quality, carcass traits and blood constituents. One hundred and eight 26-weeks old, commercial Hy-line Brown hens were randomly assigned into 3 groups, (six replicates of six birds each). The basal diet was formulated to meet requirements of layers and supplemented with dried yeast (Saccharomyces cerevisiae) at levels of 0, 3 or 6 g / kg feed and fed for four months. Results showed that yeast supplementation at levels of 3 or 6 g / kg feed significantly decreased hen/day egg production, egg number and feed consumption. Dried yeast at 6 g /kg diet tends to decrease live weight, heart weight and plasma total protein. In conclusions yeast supplementation significantly increased shell thickness and improved shell% and yolk. Meanwhile, haugh unit, albumin, egg shape index and yolk index did not significantly affect.