The present experiment was conducted for 45 days to evaluate the effect of dietary selenium on haematological parameters. Experiment was conducted in glass aquariums of size 0.75 m X 0.45m X 0.45m. All treatments were carried out in triplicates. Four numbers of experimental selenium incorporated diets were prepared including control which are as follows Control (0 mg organic selenium/kg of diet), T1 (2.5 mg organic selenium/kg of diet), T2 (5.0 mg organic selenium/kg of diet) and T3 (10 mg organic selenium/kg of diet). During the experiment, the water quality parameters (temperature, DO, pH, conductivity, hardness, ammonia, nitrate and nitrite) were found to be insignificant (P<0.05) among all the treatments. RBC’s count in T1 (4.90 million/mm3) was significantly (P<0.05) higher than Control and T3. The value of WBC’s count in T1 (1.58 thousands/mm3) was significantly (P<0.05) higher from that of T2 and T3. Haemoglobin level in T1 (6.41 g/dl) was also significantly (P<0.05) higher from T3. (185.88%). The result of the present study indicated that the experimental diet containing 2.5 mg organic selenium/kg of diet appears to be suitable for improved haematological parameters compared to the other treatments.