Background: One of the important by-products is sesame seed meal; it is a by-product of sesame seed pressing. Sesame oil cake or meal is a relatively good source of crude protein which can replace part of basic ingredients in diets such as soybean. Method: Fifteen growing male Barki lambs aged 5-6 months (18.50 ± 0.98 kg) were used to investigate the influence of replacing soybean meal (SBM) that incorporated (16% of control ration) sesame meal (SM) at 50% or 100% on feed and water intakes, nutrient digestibility, growth performance, rumen parameters, and economic evaluation. Lambs received one of the three tested complete feed mixtures that contained 16% SBM (R 1), replaced 50% of SBM with SM (R 2), contained (8% SBM + 8% SM) or completely replaced 100% of SBM with SM (R 3) and contained 16% SM. Results: Dietary treatments had no significant effect on all nutrient digestibility and total digestible nutrients value, meanwhile it decreased (P < 0.05) their contents of digestable crud protine when SBM was completely replaced by SM. Average daily gain (ADG) increased (P < 0.05) while increasing the level of replacement SBM by SM. Feed conversion expressed as g. gain improved (P < 0.05) with the increasing level of inclusion SM in the rations. Ruminal pH values increased (P < 0.05), meanwhile, values of NH 3-N concentration insignificantly decreased; however, values of total volatile fatty acid concentration insignificantly increased when SBM was replaced at half or completely by SM. Economical efficiency improved by 147.9% and 163.5% for R 2 and R 3 compared to control (R 1). Conclusion: It can be mentioned that SM is a good source of protein and can be successfully used as an unconventional source in growing lamb rations without causing any deleterious effect on their performance, digestibility, and ruminal fermentation while realizing a decrease in feed cost with improving economic efficiency, so it can incorporate SM in sheep rations to improve profitability or net revenue and decrease feed cost/kg gain.