Exogenous fibrolytic enzyme (EFE) have been shown to increase daily gain and feed efficiency in feedlot animals.  So, this study aimed to evaluate effect of using EFE on productive performance of growing lambs. sixteen Barkey lambs (3 months old, 22.31± 1.57 kg) were randomly assigned into two groups, 8 lambs for each according to live body weight. The first group (control) was fed control rations without EFE supplementation, while treated group were fed the control ration plus 2.5 g exogenous fibrolytic enzyme. The groups fed ration supplemented with EFE recorded higher DM, TDN and digestible CP intake. Supplementation of lambs ration with EFE showed no significantly effect on rumen liquor TVFA's and ammonia concentration at 0, 3 and 6 hrs post feeding. While Supplementation of lambs ration with EFE significantly increased rumen liquor pH at 0, 3 and 6 hrs after feeding compared to the control group. Exogenous fibrolytic enzyme significantly improved nutrients digestibility as dry matter, organic matter, crude protein, crude fiber, nitrogen free extract, neutral detergent fiber (NDF) and acid detergent fiber (ADF) as well as feeding values as TDN and digestible crude protein. Exogenous fibrolytic enzyme supplementation to lambs ration showed numerically increased (P>0.05) in plasma total protein concentration compared to lambs fed ration not supplemented. While albumin, globulin, triglycerides  and creatinine concentration and Alanine Transaminase(ALT), Aspartate Transaminase(AST), alkaline phosphates activity were not significantly (P>0.05) affected by Direct-Fed Microbial (DFM) supplementation. Total gain and average daily gain significantly increased (P≤0.05) for group received rations supplemented with EFE compared to control group. Also supplementation lambs rations with EFE significantly (P≤0.05) improved feed conversion as DM, TDN, CP and DCP compared to the control group. It could be concluded that supplementing lambs ration with EFE resulted in increase feed intake and digestibility, consequently increased average daily gain and feed conversion without any adverse effect on animal health and performance.