The aim of this study was to investigate the effect of Grow K Probio (commercial product) supplementation in the rations of growing lambs at different levels on performance, digestion coefficients, nutritive values, nitrogen utilization, daily gain, feed conversion and economic efficiency. Twenty-four Frafra lambs (23.70 + 2.56 Kg body weight) were randomly distributed into four groups, each with six animals. The first group was a control group and animals fed on1 kg concentrate feed mixture (CFM) and 1% Alfalfa hay of live body weight (LBW), while animal in groups T1, T2 and T3 fed the same control diet supplemented with 2.5, 5 and 7.5 g/h/d commercial probiotic (Grow K Probio/h/day), respectively. The feeding trial lasted for 120 days for average daily gain, feed intake and fed conversion ratio measurements. Four digestibility trials were also carried out using twelve local rams randomly assigned into four groups (4 rams/trial) for nutrients digestibility, nutritive values and nitrogen utilization measurements. Results indicated that the digestibility of all nutrients and feeding value of experimental rations containing Grow K Probio increased (P<0.05) with increasing the level of Grow K Probio supplementation as compared to the control ration. Daily dry matter intake expressed as DM and TDNwas significantly (P<0.05) higher in lambs fed rations containing different levels of Grow K Probio than those fed control ration. Lambs received 5 g/h/d Grow K Probio recorded highest (P<0.05) average daily weight gain (ADG) than those received other Grow K Probio levels and control ration. The lambs fed different levels of probiotic (Grow K Probio) had (P<0.05) significant effect, on rumen NH3-N and total volatile fatty acids. However, rumen pH not affected. Feed conversion and economic efficiency of lambs fed T2 and T1 were improved when compared with T3 and control groups. It could be concluded that, supplementation of probiotics particularly with the level 5 g /h/d probiotic (Grow K Probio) to growing lambs improve nutrient digestibility, daily gain, feed conversion and economic efficiency as compared with other groups.