The objective of this study was to determine the effects of dietary yeast cell wall (YCW) on performance, egg quality, some blood parameters and humoral immune response of laying hens during 26 wks period. For this purpose a total of 225 Hyline Brown laying hens, 39 wks of age, were allocated to one control group and four treatment groups. Basal diet was supplemented with YCW derived from bakers yeast Saccharomyces cerevisiae (InteMOS) at the level of 1, 2, 3 and 4 g/kg in the diets of the first, second, third and fourth treatment groups, respectively. Dietary treatments did not significantly affect body weight, feed intake, egg production, egg weight, feed conversion, and egg internal and external quality characteristics. YCW supplementation at the level of 1 and 2 g/kg decreased egg yolk cholesterol level as mg per g yolk (P < 0.05). Blood serum levels of cholesterol and triglyceride were decreased with the dietary inclusion of YCW at the level of 2, 3 and 4 g/kg (P < 0.01). Dietary YCW supplementation increased antibody titres to SRBC (P < 0.01). As a result dietary YCW at the level of 1 and 2 g/kg had beneficial effects in the production of low cholesterol eggs and improvement in humoral immunity response.