A total number of 32 of Ossimi lambs averaged 29.25 ± 2.02 kg and 4 months old were used in this experiment to compare the effects of dietary supplementation of inorganic selenium (sodium selenite), organic selenium (Se-yeast) and Nano-Se particles on nutrients digestibility, nutritive value, productive performance and serum biochemical indices of lambs. The animals were allocated into four equal groups (8 lambs each). The lambs of control group were fed on basal diet containing 0.17 mg Se/kg dry matter (DM). The treated lamb groups fed on the same basal diet, in which Se at 0.30 mg/kg DM was provided as sodium selenite (SS), selenium yeast (SY) and Nano-Se particles (NS). The results showed that digestibility of DM was higher (P<0.05) for lambs fed SS, SY and NS than those fed control. Digestibility of OM, CP, CF, EE, NFE and the values of digestible crude protein (DCP) and total digestible nutrients (TDN) were increased (P<0.05) for lambs fed SY and NS compared with those fed SS or control. Averages of final body weight (FBW) were increased (P<0.05) for lambs fed SY and NS compared with those fed SS and control. Average of FBW was greater (P<0.05) for lambs fed NS than those fed SY. The averages of daily gain (ADG) were increased (P<0.05) for lambs fed SS, SY and NS vs. those fed control with significant (P<0.05) differences among treatments. No significant differences were detected in averages of feed intakes of Alfalfa, DM and total DM (TDM) for lambs fed SS, SY and NS vs. control. While, the intakes of DCP and TDN were greater (P<0.05) for lambs fed SS, SY and NS vs. those fed control with significant (P<0.05) differences among treatments. The averages of feed conversion (FC) of DM (FC-DM), DCP (FC-DCP) and TDN (FC-TDN) were improved (P<0.05) for lambs fed SS, SY and NS vs. those fed control. The highest values of productive performance parameters (FBW, ADG, DCPI, TDNI, FC-DCP and FC-TDN) were noticed for lambs fed NS followed by those fed SY and then SS and control. Lambs fed SY and NS had higher (P<0.05) values of serum total protein and globulin than those fed SS or control. Also, there was an increase (P<0.05) in serum glucose concentrations for lambs fed diets SS, SY and NS vs. control, with higher levels (P<0.05) in NS than in SS and SY. No significant differences were noticed in serum concentrations of albumin, cholesterol, alanine transaminase (ALT) and aspartate transaminase (AST) enzyme activities. Serum total antioxidant capacity (TAC) concentrations, glutathione peroxidase (GSH-Px) activity and testosterone levels were increased (P<0.05) for lambs fed SS, SY and NS vs. control. Higher (P<0.05) levels of TAC, GSH-Px and testosterone levels were observed for lambs fed NS than those fed SS and SY. It could be concluded that dietary supplementation of Nano-Se was more effective than sodium selenite and Se-yeast to improve nutrients digestibility, feeding values, growth performance, some serum metabolic indices, antioxidant status and reproductive efficiency of male lambs.