This study was carried out to determine the effects of dietary yeast cell wall supplementation on growth performance, carcass traits, antibody production to sheep red blood cells (SRBC) and histopathological changes in broilers. A total of 272 Ross 308 male broiler chicks aged one day were allocated into one control group and three treatment groups each containing 68 chicks. A basal diet was supplemented with 0, 1, 2 and 3 g/kg yeast cell wall (InteMos) to obtain dietary treatments. The experimental period lasted 6 weeks. Dietary yeast cell wall increased body weight gain during the first three weeks (P<0.001). Feed conversion during the first three weeks (P<0.001) and during the overall experimental period (P<0.01) were improved with the dietary supplementation of yeast cell wall. No differences were observed in feed intake, carcass yield and the relative weights of gizzard, liver and heart. Yeast cell wall supplementation decreased the relative weight of abdominal fat (P<0.05) and increased antibody titres to SRBC (P<0.01) in broilers. Control and treatment groups had similar histological grade; hepatic lobular inflammation, steatosis and cell ballooning scores and, cardiac steatosis. It is concluded that yeast cell wall was an effective feed additive in broiler feeding due to the increased growth performance, increased humoral immune response and the reduction in abdominal fat.