The aim of the present study was to determine the effect of supplemental two sources of selenium; inorganic and nano (Se-NP), on growth, nutrients digestibility, immunity, and carcass traits of New Zealand White (NZW) rabbits. A total of 45 male rabbits (5 weeks old) at average body weight of 582.46±7.52g were divided into three groups (15 rabbits/group) fed the following diet group: 1) the basal diet as control diet, 2) the basal diet+sodium selenite (0.3 mg Se/kg diet), and 3) the basal diet+ Se-NP (0.3 mg Se/kg diet), during period from 5 to 13 weeks of age. The findings showed that final body weight, relative growth rate, daily weight gain, and daily feed intake were significantly (P<0.05) higher in the rabbit fed diets supplemented with organic Se and Se-NP than those of the control group. Se-NP supplementation had improved feed conversion ratio, nutrients digestibility, nutritive values, and hemoglobin concentration in comparison with other groups. Additionally, the highest values of profit margin were observed in the rabbits fed diets supplemented with Se-NP. There were no histological abnormalities in the architecture of liver and kidney tissue in the experimental groups, indicating that the tested doses of Se were safe. In conclusion, supplementing fattening rabbit diets with Se-NP was significantly better than inorganic selenium in enhancing feed utilization, growth performance, nutrients digestibility and economic efficiency without any negative effect on architecture of liver and kidney so it could be used safely.