Xylanase supplementation can improve nutrient digestibility in pig diets by degrading cell wall non-starch polysaccharides and reducing digesta viscosity as well as promoting intestinal health of pigs after weaning. This study looked at the effects of dietary xylanase supplementation on growth performance, apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients, and digesta viscosity in different digestive sites of weaned pigs. A total of 312 weaned pigs (BW 5.1 ± 0.9 kg) were weaned into 48 pens and assigned to one of six dietary treatments, each treatment with 8 pens, 6-7 pigs per pen, and sex ratios maintained within BW blocks. Experimental diets were formulated in a 3-phase nursery feeding program: Phase 1 (d0-d7), Phase 2 (d8-d21), and Phase 3 (d22-d42). Experimental diets consisted of a wheat/soybean meal-based diet formulated to meet pig requirements (positive control, PC), the PC diet with reduction of 100 kcal of ME (negative control, NC), and the NC diet supplemented with either 900, 1800, 3600, or 7200 units of xylanase. Feed disappearance and body weight were measured at d7, 14, 21, and 42. Pen fecal score was assessed daily during d 0 to 14 and three times a week during d 15 to 28. On d21 to 24 of the experiment (12 pigs per day), one pig per pen was selected for sample collection: ileal, cecal, and mid-colon digesta for viscosity and ileal digesta and feces for nutrient digestibility. Orthogonal polynomial contrasts were used to determine the linear and quadratic effects of increasing levels of xylanase in NC diets. Contrast analysis was used to compare PC and NC groups with xylanase-supplemented groups. Fecal scores data were analyzed using the PROC FREQ procedure. Supplementing xylanase to NC diets did not improve pig growth performance (P > 0.05) through the nursery period. In Week 2 and Week 3, pigs fed the PC and NC diets had a greater (χ2 < 0.05) incidence of fecal scores 3 & 4 (diarrhea) than the xylanase-supplemented pigs. The AID of DM and ATTD of crude protein, gross energy, and NDF were greater (P < 0.05) in the PC and 900-xylanase supplemented diets than in the other dietary treatments. In addition, the ATTD of NDF and ADF increased linearly (P < 0.1) in response to xylanase supplementation. Xylanase supplementation (900 to 7200 U) decreased digesta viscosity in colon when compared to PC and NC diets.