Background: Nutritional strategies targeting improvement of poultry performance and disease prevention are currently being developed and in this respect the dietary intake of spiced essential oils and pre-biotics in raising broilers is receiving attention. OBJECTIVES: This study was conducted to compare the effects of diet containing ginger essential oils (GEO) and mannan-oligosaccharide (MOS) on growth performance,  biochemical and hematological parameters, lymphoid organ weights and antibody response of broilers. METHODS: A total of 375 day old male broiler chicks were randomly assigned to five treatments (five replicates per treatment). Dietary treatments included basal diet as control, GEO-supplemented diets with inclusion levels of 50 (GEO1), 100 (GEO2) or 200 (GEO3) mg/kg, and MOS supplemented diet with an inclusion level of 2 g/kg. RESULTS: The birds fed on MOS and GEO3 diets exhibited better feed conversion ratio and higher body weight gain from 1 to 42 day of age compared with control birds (p<0.05). Serum low density lipoprotein cholesterol level in the MOS, GEO2 or GEO3 groups was lower than that of the control group (p<0.05). Serum cholesterol level was also lower in the GEO2 and MOS groups (p<0.05). Feeding on GEO3 and MOS diets significantly increased relative bursa weight and secondary antibody titer against infectious bursal disease (IBD) and infectious bronchitis (IB) vaccines as compared with control diet (p<0.05). CONCLUSIONS: The results showed that higher level of GEO (200 g/kg) similar to MOS supplementation, improved feed efficiency and immune response. This could meet consumers’ demand for a safe feed additive.