Selenium, a trace mineral complement is used as cofactor of antioxidant enzymes that protects fishes against environmental stress agents and enhances performance in fishes. In this study the different levels of organic and inorganic source of  selenium were included in juvenile rainbow trout diet to evaluate feed conversion ratio (FCR), specific growth rate (SGR), weight gain percent (WG), condition factor (CF), survival rate (SR) and proximate analysis of the fillet during 60 days of the experiment. The fishes were allotted to 9 treatment groups including, Tc the fishes were fed diet without any selenium, control group, To1, To2 ,To3 and To4 the fishes were fed different dosages of inorganic selenium and Ti1, Ti2, Ti3 and Ti4 those were fed different dose of inorganic Se in their diet. Results showed that To4, showed the highest level of WG from 50±2.8 to 168.54± 25.56 g in comparison to Tc (134.38± 27.26g) (p<0.05). Average initial total length of fishes (19± 1.12 centimeters) increased to 21.1± 1.12 cm in Tc and 22.46± 1.25 cm in To4 significantly (p<0.05). Among all treatments, FCR, SGR, WG, CF and SR were improved in To3 group. Also carcass protein increased in To4 (32.58±1.22%) on the contrary of Ti4 (22.43±1.51%) (p<0.05).  As a general conclusion, dietary incorporation of organic selenium at 0.45 mg/kg showed satisfactory results in some growth parameters and was a useful supplement in salmonid fish diets.