The current study examined the effects of probiotics (Pronifer and More-yeast) supplementation to growing lambs. 25 crossbred (Osimi×Rahmani) growing lambs of about 6-8 months age and an average initial live body weight of 25 kg were used. Lambs divided into five groups (5 lambs for each group) and the experimental period lasted for 169 days. The control group T1 received concentrate feed mixture (CFM), group T2 and T3 received 1.5 and 3 kg Pronifer/Mg (megagram) CFM and group T4 and T5 received 2.5 and 5 kg More-yeast/ Mg CFM, respectively. Rumen liquor and blood samples were taken and digestibility trial was conducted at the end of the experiment. Results showed higher digestibility values for crude protein (P<0.05) in T3 and T4 when compared to control. Nutritive ratio was lower (P<0.05) in groups T3 and T4 than in group T2. More-yeast supplementation improved dry matter intake (P<0.001), while a reverse trend was observed with Pronifer supplementation. All treatments had little effect on ruminal liquor except ruminal ammonia concentration in T5 was lower (P<0.05) than other treatments. The differences in most blood plasma parameters due to treatment effect were not significant, except plasma urea and globulin concentrations increased (P<0.05) with T5 treatment. The obtained results appear to indicate that Moreyeast supplementation improved lambs performance and digestibility, whereas, Pronifer supplementation enhanced digestibility.