Hematological parameters (Ht, Hb, RBC, WBC, PLT), erythrocyte size, and osmotic fragility, differential leukocyte count, ROS production in common carp blood collected on three anticoagulants: heparin (10 IU/mL, Na2EDTA (0.1, 0.5, and 1 mg/mL), and sodium citrate (0.3 mg/mL) were compared. Na2EDTA caused partial blood hemolysis in Ht tubes which made Ht measurement impossible, and resulted in high variability of the results. Both, citrate and Na2EDTA increased sensitivity of red blood cells to hemolysis. Na2EDTA also induced erythrocyte anisocytosis and anisonucleosis. Na2EDTA significantly increased ROS production but no effect of anticoagulants on WBC, PLT or differential leukocyte count was observed. The obtained results show that Na2EDTA should not be used for evaluation of red blood cell parameters and erythrocyte morphology, and for ROS production measurement in common carp. Heparin proved to be the most appropriate anticoagulant to use for this species, although Na2EDTA and sodium citrate may be used for WBC and leukocyte differential count evaluations.