In this study, the effects of beta-glucan administration at different dosages on non-specific immune response and haematological parameters in healthy Nile tilapia (Oreochromis niloticus L.) were investigated. Fish were fed with diets containing 0.5% and 0.1% glucan (experiment) and without glucan (control) for 2 weeks. After feeding for 2 weeks with 2 different dosages, erythrocyte (RBC), leukocyte (WBC), hematocrit (Hct), haemoglobin (Hb) amount, leukocyte cell types (percentage of lymphocyte, monocyte, neutrophil, eosinophil), the values of phagocytic activities, erythrocyte cell indexes (MCV and MCH) and blood cell sizes were determined. WBC and phagocytic activity amounts, percentages of lymphocyte and monocyte of fish fed with the diets containing 0.1% glucan were higher than 0.5% glucan and control groups (P < 0.05). RBC amount was found to be higher in the experimental groups than in the control group. There were no differences between groups in terms of Hb, Hct, MCV, MCH, neutrophil, eosinophil, and cell sizes values (P > 0.05).