This study was performed to investigate the effects of dietary supplementation of synbiotic on intestinal morphology, hepatic enzyme activity, serum immunoglobulin level and growth performance in broilers. A total of 720 one-day old Cobb 500 broiler chickens were randomly assigned to 4 treatment groups as control, dose 1 (500 g/ton), dose 2 (1000 g/ton) and dose 3 (2000 g/ton) diet supplementation of synbiotic. The synbiotic included Saccharomyces cerevisiae strain NCYC R618 (4x10(12) CFU/kg), mannan-oligosaccharide (88000 mg/kg) and glucan-oligosaccharide (96000 mg/kg). Each experimental group consisted of 6 replicates containing 30 chickens (15 female, 15 male). At 42 days of age, body weight of broilers fed with dose 2 diet was found to be highest with a value of 3239 g, when compared control, dose 1 and 3 groups (2819, 3009 and 2981 g, respectively, P<0.01). Feed conversion ratio was found to be the most efficient with a value of 1.72 in the dose 2 group (P<0.01). An increased activity of AST and ALP were observed in broilers fed with dose 2 diet (467 and 476 IU/l, respectively, P<0.01) compared to the other groups. The highest concentration of T3 and the lowest concentration of T4 were found in the control group (3.3 ng/ml and 7.3 mu g/dl, respectively). Morphological changes in jejenum including villus height, crypt depth, Tunica muscularis and villus apparent surface area were clearly stimulated with synbiotic supplementation. Interestingly, supplementation of synbiotic enhanced jejunal villus apparent surface area by about 54.4%, 95.4% and 74.9% in dose 1, 2 and 3 groups, when compared to the control group. These findings demonstrated that dietary supplementation with synbiotic has a potential for improving broiler performance by increasing body weight and intestinal villus development.