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An experiment using 48 male lambs (average body weight 23.8±2.2 Kg, 172±5 days old), was conducted to investigate the effect of different levels of clinoptilolite (natural zeolite, CL) on average daily gain (ADG), dry matter intake (DM1), feed conversion ratio (FCR), nutrient digestibility, and carcass characteristics. The dietary treatments were the basal diet (BD) as control, (0% CL) and BD plus 2, 4 and 6% Clino (CLI) on a dry matter basis. A complete randomized block design was employed in the research. The lambs were divided according to their initial live weight into three groups (blocks) and were fed total mixed rations (TMR) individually and ad-libitum. At the end of the experiment, lambs were slaughtered, and carcass physical cuts as well as chemical composition of boneless 10, 11, 12th ribs were determined. Dry matter (DM)) crude protein (CP), ether extract (EE), neutral degergent fiber (NDF), and apparent digestibility (D) were determined. The results showed that ADG, FCR (P<0.05), crude protein (Kg CP/Kg gain) and metabolizable energy (Mcal ME/Kg gain) conversion ratios (P<0.0 1) were significantly improved by using CLI. The lambs which received the 4% CLI diet had the highest ADG (196.92 gr), best FCR (7.07 and 6.70, respectively), CP and ME conversion ratios (0.99 and 17.67, respectively), while those, which received control, diet had the lowest ADG (166.91 gr), the worst FCR (8.03), CP and ME conversion ratios (1.18 and 20.89, respectively). Average DM1 was not affected by dietary treatments. Apparent digestibility of DM, EE (P<0.0 1) and CP (P<0.05) were significantly affected by dietary treatments. The 2% CLI diet had the highest DMD and EED (65.48 and 65.84%, respectively) while the 4% CLI diet had the highest CPD (63.38%). The 6% CLI diet had the lowest DMD (56.49%) and control diet had the lowest EED and CPD (57.90 and 5 5.63%, respectively). Apparent digestibility of NDF improved by addition of CLI to the diet. Carcass weight, fill and empty body dressing percentages were not affected by dietary treatments. Average CP%, CP/Moisture (P<0.01) and CP/EE ratios (P<0.05) of boneless 10, 11, 12th ribs increased by addition of CLI to the diet. The control diet had the lowest CP%, CP/Moisture and CP/EE ratios (14.3%, 0.27 and 0.46, respectively). CLI Supplementation of diet decreased EE% and increased ash percentage of boneless 10, 11, 12th ribs. Addition of 4% CLI to diet decreased feed cost by 13.4% as compared to control (3811 and 4402 Rials / Kg gain, respectively). In general, from an economic viewpoint, addition of CLI to diet decreased feed cost.