The recognition that chitooligosaccharide (COS) possess potent anti-inflammatory, antioxidant and antimicrobial properties has prompted studies investigating its efficacy for animal growth and intestinal health. The objective of this study was to examine the effect of COS on growth and jejunal barrier function of weaning piglets. A total of 18 piglets (6.55 ± 0.32 kg) at 21 d of age, were randomly assigned to 1 of 3 groups (n = 6/group). Piglets in group 1 continued to be nursed by sows, while piglets in groups 2 and 3 were weaned to a corn and soybean meal–based diet that was supplemented with 0 mL or 10 mL COS (5 ml/time, 2 times/d). At 28 d of age, growth performance, jejunal structure and epithelial integrity were examined. Data were analyzed by ANOVA procedure of SPSS. Differences between means were determined by using the Duncan multiple comparison method. The results indicated that final BW and ADG were markedly reduced in weanling piglets when compared with suckling piglets (P < 0.05), while supplementation with COS restored ADFI, final BW and ADG in the weaned piglets (P < 0.05). Weaning stress did not affect villous height but increased crypt depth and decreased the ration of villous height: crypt depth (P < 0.05), whereas, this alteration can’t be reversed by COS supplementation. Peripheral D-lactate concentration and diamine oxidase activities were not affected by weaning stress or COS supplementation. Weaning stress led to greater jejunal cell apoptosis index and sIgA content (P < 0.05), and COS supplementation partially restored this changes (P < 0.05). Jejunal gene abundance of occludin was not affected by weaning or COS supplementation, while the weaning-induced decrease in jejunal ZO1 (P < 0.05) and ZO2 mRNA levels were elevated by COS supplementation (P < 0.05). Collectively, our results support an important role of COS in regulating jejunal barrier function of weaning piglets.