This study was conducted to investigate the effects of different levels of prebiotic (Immunoster) on the blood parameters and immune response of the common carp (Cyprinus carpio). For this purpose, a total of 300 juvenile common carp (24.9±0.52g) were randomly divided into four groups in triplicates and each group was fed with diets supplemented with prebiotic (Immunoster) at the dose level of 0, 0.5, 1.5 and 2.5 g/kg for eight weeks. At the end of the experiment, the blood parameters including white blood cell Count (WBC), red blood cell count (RBC), hematocrit (PCV), hemoglobin (Hb), globular indexes (MCV; MCH and MCHC) and differential counts of WBC, as well as total protein. The immune responses included antibactericidal and lysozyme activities. The results indicated that in spite of the increase in some of the immunological indices in the fish, fed with the food including Immunoster, there were no significant differences in the blood and immunological indices. It can be concluded that the use of 0.5, 1.5 and 2.5 g/kg of Immunoster had no significant effect on the blood parameters and immune response of the common carp.