Fifteen weaning Rahmani lambs with an average live body weight 19±0.5 kg and 4 months age were randomly assigned into three groups (each of 5 lambs) to study the effect of heat protected soybean meal protein diets at 145°C in a forced air oven for 4 hrs on nutrients digestibility as well as feeding values and their reflection on growth performance of growing lambs. Animals were fed for 120 days feeding period on the same three experimental diets. Control fed diet containing soybean meal (15%) without treatment as a consists of CFM + clover hay. The T1 fed diet containing (50% soybean meal protected + 50% soybean meal unprotected) as consists of CFM + clover hay. The T2 fed diet containing 100% soybean meal protected as consists of CFM + clover hay animal were fed in groups. Digestibility coefficients were determined using acid insoluble ash (AIA%) as natural marker. The obtained results indicated that digestibility coefficients of DM, OM, CP, EE and NFE for lambs fed heat protected soybean meal protein were higher than those fed untreated diet. The improvements in nutrients digestibility reflected better feeding values in terms of TDN and DCP% for both diets contained treated protein than untreated one. Total dry matter intake varied between 1475.85 to 1518.28, 86.02 to 93.66 and 3.30 to 3.70 expressed as g/h/day, Kg W0.75 and %BW, respectively. In average, it is clearly appears that the highest daily weight gain was showed in T2 followed by T1 and control diets (0.211±0.013, 0.172±0.009 and 0.159±0.015Kg, respectively). The changes in body weights were in ascending order with increasing the level of protected soybean meal protein in animal diets. Net revenue was pronouncedly higher in diet that included heat protected soybean meal protein (853.634 and 1129.2 for T1 and T2, respectively) while it was 761.400L.E in control diet. From the obtained results, this study recommends the use of heat treatment as a protection method for SBM protein diets in growing lambs at 100% protected soybean meal protein.