Simple SummaryThis study assessed the effect ofPiper sarmentosumextract addition on the growth performance, intestinal barrier function, and metabolism of growing chickens. It was found that dietary supplementation withPiper sarmentosumextract could enhance the anti-inflammatory capacity and intestinal mucosal barrier function of growing chickens.AbstractIn the poultry industry, there is an urgent need to evaluate and introduce natural, effective, and safe alternatives for synthetic antibiotics, which have been banned in most countries. The present study aimed to investigate the effects of dietary supplementation withPiper sarmentosumextract (PSE) on the growth performance, intestinal barrier function, and metabolism of growing chickens. A total of 400 seven-day-old female chicks were randomly assigned to four dietary treatments, each of which consisted of five replicates and twenty birds each. The four experimental treatments were fed a basal diet containing 0, 100, 200, and 300 mg PSE/kg (BC, PSE1, PSE2, and PSE3 groups), respectively. The experiment lasted for 28 days. The results showed that dietary supplementation with PSE had no significant effects on the final body weight, average daily gain (ADG), average daily feed intake (ADFI), and the ratio of ADFI to ADG (F/G) (p> 0.05). Compared with the BC group, dietary supplementation with 200–300 mg/kg PSE increased the villus height in the jejunum and ileum of chickens (p< 0.05). The PSE-treated groups significantly increased the mRNA expression ofOccludin,ZO-1, andClaudin-1in the ileal mucosa of chickens (p< 0.05). In addition, a significant decrease in ileal TNF-α and IL-8 mRNA expression (p< 0.05) and a significant increase in IL-22 (p< 0.05) were observed in the PSE2 treatment compared to the BC group. Additionally, three gut metabolites (i.e., citrate, isocitrate, and spermine) showed significant differences among treatments (p< 0.05) and were involved in the tricarboxylic acid (TCA) cycle, the transfer of acetyl groups into mitochondria, and spermidine and spermine biosynthesis, respectively. In conclusion, the findings obtained here indicate that supplemental PSE can enhance the anti-inflammatory capacity and intestinal mucosal barrier function of chickens.