Background:This study evaluated the effects of supplemental xylanase and xylooligosaccharides (XOS) in a corn-soybean meal (SBM)-based diet on growth performance and intestinal health of broilers. A total of 288 day-old chicks (Cobb 500) were allocated to 36 floor pens (8 birds/pen) equally in 9 dietary treatments in a 3 × 3 factorial arrangement. The treatments were combinations of 3 levels of xylanase (0, 0.005％and 0.01％Econase XT) and 3 levels of prebiotics (0, 0.005％and 0.01％XOS) added to basal mash diets formulated in three phases (starter, d 0–14;grower, d 15–28;finisher, d 29–42). The feed intake and body weights were recorded weekly. On d 42, ileal sections were collected for histomorphometric and gene expression analysis, and cecal content was collected for determining short-chain fatty acids (SCFA) and microbiota. Results:Xylanase linearly (P0.05). Supplemental xylanase and XOS did not affect average daily feed intake and feed conversion ratio (P>0.05). Xylanase and XOS did not change villus height (VH) or crypt depth (CD) ratio (P>0.05). However, xylanase exhibited a trend (P=0.097) on VH:CD ratio. The inclusion of 0.01％XOS without xylanase increased the level of IL-10 (a marker of anti-inflammatory cytokine) and IL-4 (a T-cell differentiation cytokine) genes compared with control (P<0.05). The acetate production was increased by xylanase (P<0.01) and XOS (P<0.05) without an additive effect. Xylanase increased total SCFA (P0.05). However, the mean proportion of family Ruminococcaceae was increased by the supplemental 0.01％xylanase (P<0.01). Conclusion:It can be concluded that XOS can enhance cecal fermentation, while xylanase can increase the body weight gain along with the fermentation metabolites in the ceca of broilers fed the corn-SBM-based diet but the effects may not always translate into an improved mucosal absorptive capacity and a better feed efficiency.