The trial was conducted to investigate effects of grape seed procyanidins (GSP) on growth performance, immune function and antioxidant capacity in weaned piglets. A total of 160 Duroc×Landrace×Yorkshine piglets weaned at 21 days of age (body weight, 6.99±0.11kg) were randomly assigned to one of the five treatment groups with 4 replicate pens per group and 8 piglets per pen. The treatments included control group (fed a basal corn–soybean meal diet, BD), antibiotics group (BD+20mg/kg of flavomycin+100mg/kg of aureomycin), and three different GSP level groups (BD+50, 100, 150mg/kg GSP respectively). The trial lasted 28 days. Diarrhea scores were recorded daily, and the average daily gain (ADG), average daily feed intake (ADFI) and feed/gain ratio (F:G) were calculated. Blood samples were collected on d 14 and 28 for the measurement of serum immune parameters and antioxidant indices. Dietary GSP or antibiotics supplementation did not exert significant effects on ADG, ADFI and F/G during overall experimental period. As compared with the control group, supplementation with antibiotics or different levels of GSP decreased the diarrhea incidences in piglets significantly (P<0.05). Pigs offered diets supplemented with GSP at doses of 100 or 150mg/kg generated higher (P<0.05) serum immunoglobulin (Ig) G, IgM, complement 4 (C4) and interleukin-2 (IL-2) concentrations, produced stronger (P<0.05) serum total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities and lower serum malondialdehyde (MDA) content than those fed basal diet or antibiotics diet. In conclusion, administration of GSP in weaned piglets diet had no effect on the growth performance during the whole experiment. However, the beneficial effects on diarrhea incidences, immune responses and antioxidant abilities suggested that GSP has a positive role in weaned piglets.