An experiment was conducted to compare the effect of organic (selenized yeast) and inorganic (Na-selenite) selenium on nutrient digestibility, growth performance and blood parameters of growing buffalo claves. Fifteen Egyptian healthy male buffalo calves were divided randomly into three groups (5 animals each). The treatment groups were as follows: control group (G1) fed basal diet without selenium supplement and treated groups fed 0.22 mg Se/kg DM as either Na –Selenite (G2) or selenized yeast (G3) to the concentrate mixture. All animals were fed 70% of their requirements as concentrate mixture, while wheat straw given as roughages ad libitumThe results indicated that there were significant (P<0.05)  improvements in the digestibility coefficient of organic matter, crude protein, either extract and crude fibre due to dietary supplementation of both Se- yeast and Na-Selenite. No significant differences were observed in growth rate and total dry matter intake of calves between treatments groups. Dietary Se-yeast and Na-selenite supplementation led to significantly (P<0.05) improved fed conversion ratio for calves as compared with control group (10.86 and 11.09 vs. 11.99). Calves fed Se-yeast or Na-Selenite supplement had increased (P< 0.05) concentrations of selenium in whole blood, greater activity (P < 0.05) of blood glutathione peroxidase (GSH-Px) with lower (P< 0.05) cholesterol and urea concentration than those fed the control diet. In conclusion, dietary supplementation with Se-yeast was more effective than sodium selenite in improving nutrient digestibility, feed conversion efficiency and increasing both Se concentration and GSH-Px activity in the blood of buffalo calves.