This study was carried out to investigate the effect of inclusion of dietary supplementation of some medicinal plant (oregano, rosemary and peppermint)on nutrient digestibility, rumen fermentation, blood metabolites and performance of finishing lambs. Twenty-four Saidi male lambs with average body weight of 39.44 ± 0.61 kg were randomly distributed into four groups, each with six animals in a completely randomized design for 60 days' experimental period. The experimental groups were a control group fed basal diet containing 70% concentrate mixture plus 30 % wheat straw and treated groups was fed basal diet plus 2.5 % dried Oregano (Origanum vulgare L.) (ORG), the second group fed 2.5% dried Rosemary (Rosmarinus officinalis L.) (ROS)  and the third group was fed 2.5% dried Peppermint (Mentha piperita L) (MEN). The oregano, rosemary and peppermint  were added and mixed with concentrate mixture. Four digestibility trials were carried out using twelve rams. Inclusion oregano and rosemary were improved (P<0.05) the digestibility of crude protein as compared with control and peppermint diet. The addition medicinal plants to sheep ration increased (P<0.05) CF digestibility as compared with control one. The nutritive value of rations in terms of total digestible nutrients (TDN) and digestible crude protein (DCP) were significantly (P˂0.05) higher in medicinal plants groups than that of control group. Supplements of medicinal plants in sheep diets decreased (P<0.05) ruminal ammonia-N and total protozoal count and increased ruminal VFA's while had no effect on rumen pH when compared with the control group. It was found that no significant (P> 0.05) differences among groups in body weight, average daily gain, feed intake and feed conversion. The average value of serum total protein, globulin and total antioxidant capacity (TAC) were significantly higher in group fed medicinal plant than the control. Serum cholesterol, triglycerides and urea concentration were decreased (P<0.05) in all medicinal plant groups when compared with control group. In conclusion, supplements of some medicinal plants like oregano; rosemary and peppermint to the diets of fatting lambs at rate of  2.5% in concentrate mixture improved nutrient digestibility, feeding value and rumen fermentation. Also, the growth performance and blood biochemical parameters were improved particular with addition oregano and rosemary in fattening sheep.