The purpose of this study was to evaluate the effects of dietary supplementation of Quillaja saponin (QS) on growth performance, nutrient digestibility, fecal microbiota, and fecal gas emission in growing pigs. A total of 50 crossbred growing pigs [(Yorkshire × Landrace) × Duroc] with an initial body weight of 23.83 ± 1.95 kg were randomly assigned to one of two treatments for a 56 d trial with five replicate pens per treatment and five pigs (two barrows and three gilts) per pen. Dietary treatments including control diet and control diet supplemented with 200 mg·kg⁻¹ QS. The average daily gain was significantly increased during days 0–56, whereas the fecal ammonia emission on day 56 and fecal coliform bacteria counts on day 28 were significantly decreased in pigs fed with QS-containing diet. However, dietary supplementation of QS had no significant effects on apparent total tract digestibility. In conclusion, dietary supplementation of 200 mg·kg⁻¹ QS had beneficial effects on growth performance, fecal microbiota, and fecal gas emission in growing pigs. Considering the carry-over effects, the adaption period should be at least 28 d when supplementing 200 mg·kg⁻¹ QS to the diet of growing pigs for improving the growth performance.