In this study, the effects of beta-glucan on haematological parameters of common carp, Cyprinus carpio, which were naturally infested with ecto-parasites were determined. In the experimental group, infested fish were fed with 0.3% beta-glucan containing pellets during thirty days. In control, infested fish were fed with fish pellets without beta-glucan. Blood samples were collected from each group after feeding. Mortality rates, haemoglobin (Hb) (g/dl), haematocrite (hct) (%), erythrocyte (RBC) (x106/mm3), leukocyte (WBC) (x103/mm3) amounts and leukocyte cell types (%) were determined. In comparison with the control group, Hct and WBC amounts were increased in the fish fed with beta glucan (P <0.05), while there was no significant difference (P >0.05) for Hb and RBC amounts. Lymphocytes were decreased, while monocytes and neutrophils were increasing among the leukocyte cell types. Survival rate values were 91.12 and 77.78% for fish fed with β-1,3/1,6 glucan and the control group, respectively.