The objective of this study was to investigate the effects of replacing part of barley grain and alfalfa hay with almond hulls on performance, nutrients digestibility and feeding behavior of lambs. In this experiment, 24 lambs with an average body weight of 31 kg ± 3 were used in a completely randomized design with 3 treatments. Dietary treatments included: 0% almond hulls (control diet), 15% almond hulls, and 30% almond hulls. The diets were iso-caloric, iso-nitrogenous and iso-fibrous. The dietary geometric mean particles size was 2.98, 3.47 and 3.61 mm, for 0, 15 and 30 % almond hulls, respectively. Feed sorting index showed that lambs fed 30% almond hull sorted against particles retained on the 1.18-mm screen compared to those fed control diets. Lambs received diets containing 15 and 30% almond hull consumed more DM compared to control lambs. Average daily gain (ADG) and feed conversion ratio (feed intake/ADG) were greater in lambs received 30% almond hull compared to other treatments. Dry matter and organic matter digestibility was not affected by experimental diets, but the digestibility of neutral detergent fibers increased 30% in treatment than the other two treatments. Dry matter and OM digestibility were similar mong treatments, however, NDF digestibility was greater in diets contaning 30% almond hulls. Eating time, rumination time, rest time, eating rate and chewing rate were similar among dietary treatments, but rumination rate (expressed as min per 100 g consumed DM) tended to be lower in lambs received 30% almond hulls compared other treatments. Diets containing 30% almond hulls increased blood glucose and decreased blood urea-N concentrations compared to other treatments. Increasing almond hulls content of diets linearly increased blood total protein and globulin concentrations. The albumin to globulin ratio was lower in lambs received 15 and 30% of almond hulls compared to control treatments. Almond hulls inclusion in lamb’s diets could be considered as an option to decrease cost of diets. In addition, almond hulls at the rate of 30% decreased feed cost per kilogram ADG compared to other treatments. In conclusion, this experiment showed that almond hulls at the rate of 30 improved performance responses and decreased diets costs. Key Words almond hull, fattening, Afshari lamb, performance