In a feeding experiment lasted 70 days, the nutritional supplementation effect of Dry Moringa oleifera leaves (DML) was investigated on growth performance and rumen fermentation indices on 20 local Barki male lambs aged 6 months and weighed 24.4±1.12 kg. Lambs were randomly allocated into four equal groups where they individually fed daily on a uniform diet consisted of: 3% of body weight (BW) concentrate feed mixture (CFM) plus 1.25 kg whole corn silage and chopped rice straw fed ad-libitum. The first group (R1) was fed on un-supplemented CFM (control), while diets of R2, R3 and R4 were supplemented with 100,200 and 400 mg DML/kg BW, respectively. The offered amounts of CFM + DML were bi-weekly adjusted according to body weight change. The results illustrated that; the daily DM intake reduced by 17% with R4 diet (400mg DML) than other groups. The best (P<0.05) values of final body weight, ADG and feed conversion efficiency were recorded for lambs fed R3 diet (200mg DML), while corresponding parameters of R2(100mg ML) and control showed comparable values. With increasing DML supplementation to 400mg/kg BW (R4) ADG was remarkably fallen dawn to nearly 50% than other groups. Similar trend was achieved for nutrients digestibility and dietary nitrogen utilization, where the best results were recorded with R3 and the worst with R4. Moreover, blood plasma urea, creatinine, AST and ALT had the highest (P<0.05) values with R4 than other groups, while cholesterol was decreased (P<0.05) with increasing DML supplementation level. Ruminal NH₃-N concentration was (P<0.05) decreased with increasing DML level, while the highest TVFAs was recorded with R3 and the lowest with R4. In-vitro enteric methane production (mg/day) was decreased (P<0.05) with increasing DML supplementation level, however, the lowest CH₄ (mg/kg DMI) was recorded with R3 diet. In-vivo ruminal microbial protein had the highest yield (P<0.05) with R3 and the lowest with R4. It is worth saying that, dry Moringa oleifera leaves is useful growth promoter for lambs when supplemented at the maximum of 200mg/kg BW or in average 5 gm/day.