This study determined the effects of three levels of supplemental yeast of Saccharomyces cerevisiae var. boulardii (SCB) on commercial male poult performance and ileum morphology. One hundred and sixty Nicholas poults were randomly assigned to 16 battery cages (10 poults per cage, 4 cages per diet) from 1 to 21 d of age (DOA). Poults were fed diets (26% CP) consisting of corn-soybean (CS, control), CS + .01% SCB, CS + .02% SCB, and CS + .06% SCB. At 21 DOA, 30 poults fed the CS and CS + .02% SCB diets (from 1 to 21 DOA) were randomly selected within each diet, placed in 1 of 6 cages (5 poults per cage, 3 cages per diet), and fed their respective diet to 35 DOA. Body weights and feed consumptions (FC) were measured at 21 and 35 DOA and morphological comparisons of ileal tissues were conducted at 35 DOA. Increased BW (P < .004) at 7, 14, and 21 DOA were observed for poults fed diets containing SCB at .01, .02, and .06% of the diet. No dietary differences (P > .05) were observed in FC or feed:gain ratios from 1 to 21 DOA. Increased (P < .03) BW were maintained from 21 to 35 DOA for poults fed .02% SCB, whereas no dietary differences (P > .05) in FC or feed:gain were observed. Histological examination of ileal sections from poults (35 DOA) fed the CS and CS + .02% SCB diets revealed a decrease (P < .04) in the number of goblet cells per millimeter of villus height and a decreased (P < .02) crypt depth in poults receiving .02% SCB. No dietary differences (P > .05) were observed for either villus height or width.