Mannanoligosaccharide (MOS) have more positive effects, such as growth promotion, intestinal flora optimization, and reducing oxidative damage in broiler chickens. This study was designed to investigate the effect of dietary supplementation with MOS to improve productivity and enhance hepatic and intestinal status. Day-old chicks (n= 240) were divided into four treatments (three replicates of each) as follows: control –non supplemented group fed a basal diet recommended to strain (C), three other groups were fed a basal diet supplemented with 0.25, 0.5 and 1g MOS/kg diet, respectively. At 35 days of age, BWG, FC, FCR and EPEF were recorded. Plasma total protein, albumin, lipid profile and hepatic enzymes concentration levels were determined. Total counts of cecum microbiota and histological changes of ileum were determined. Dietary supplementation with MOS significantly improved BWG, FC, or FCR and EPEF values at levels of 0.5 and 1.0g/kg of diet compared with 0.25 level and control. Also, significant differences in plasma triglycerides and ALT levels were observed. Carcass traits were improved in supplemented groups than control. Reduction of coliforms bacteria in chicken intestine was counted with increased in villi height: crypt depth ratio. In general, dietary supplementations with different levels of MOS had a positive effect on performance and improved the gut microbial and histological status