Four groups of male lambs (seven animals/ group) were used to study the effect of natural (garlic powder; Allium sativum) and biological (dry yeast; Saccharomyces cerevisiae) additives and their combination in finishing diets as compared to control diet on feed utilization and animal performance. Animals were 8 months of age and 35.8kg ± 0. 41 as average body weight. Animals were fed a basal diet including concentrate feed mixture (CFM) at level of 70% of total requirement and berseem hay (BH) was offered ad lib. The experimental diets were: 1) a basal diet without additive (control), (C); 2) a basal diet supplemented with 6g dry yeast (2.44x1011cfu/g)/head/day, (Y); 3) a basal diet supplemented with 40g garlic powder/head/day, (G), and 4) a basal diet supplemented with 3g dry yeast plus 20g garlic powder/head/day, (YG). The results revealed that all feed additive treatments showed higher (P<0.05) digestibility values of DM, OM, CP, CF and NFE, than non-additive diet (C). The highest (P<0.05) values were observed for animals fed G diet; however, C group showed the lowest (P<0.05) digestibility values. The G diet showed the highest (P<0.05) value of TDN% (73.56%) and C showed the lowest one (69.20%). However, the DCP% was not affected (P<0.05) by additives and its values ranged between 11.81 and 12.27%. Animals fed enriched diets (Y, G and YG) showed higher ADG (180, 184 and 186 g/d, respectively) compared to control group (160g/d). Additives have no significant effect on feed intake either in the form of CFM or the roughage and consequently the total feed intake. All feed additives and their combination significantly (P<0.05) enhanced, with the same extent, the feed efficiency indicators of the enriched diets compared with control one. Yeast/garlic combined addition revealed the highest daily profit percentage relative to control (42%) followed by garlic (34.0%) and then yeast alone (31%) treatments. Energy utilization was significantly different (P<0.05) between the test groups where, the G group showed the highest values, but C group was the lowest values. When the combined additive (YG) was supplemented, N balance exhibited 15.2% increase above the control group. The concentration of blood immunoglobulins (IgA) and IgG differed (P <0.05) among groups being their concentration were enhanced by the respective additives. It could be concluded that using feed additive such as dry yeast (6 gm/h/d) or garlic powder (40 gm/h/d) or their combination (3gm plus 20 gm, respectively) in finishing diets of lamb tended to increase digestibility coefficients for most of nutrients, increasing nutritive value as TDN and appeared to increase the daily gain as well as enhanced the immune status of animals.