The effects of different levels of Whole Cottonseed (WCS) on feedlot performance and morphology of small intestine were studied in a completely randomized design with four diets containing 0, 4, 8 and 16 percent WCS on 20 Chaal male lambs for 90 days. The metabolisable energy and proteins contents of rations were equal. Number and dimensions of different types of villi and depth of crypt gland were evaluated. Different levels of WCS in the diet had no significant effect on body weight gain and feed conversion ratio, but the sheep consumed diets containing 4 % WCS more than they did the other diets (p<0.01).. The effect of diet was significant only on the number of leaf shape villi. (p<0.01). The difference number of all types of villi in different places of intestine sampling (duodenum, jejunum, ileum), also was significant. Villus dimensions and depth of crypt gland were affected by diet and sites sampling. This experiment showed that, WCS can increase villus heigh:crypt depth ratio and it could be included 16 percent of the fattening male lamb’s diet.