1. The experiment was conducted to investigate the effects of dietary sodium butyrate on the growth performance and immune response of broiler chickens. In experiment 1, 240 1-d-old chickens were allocated into 4 dietary groups (0, 0·25, 0·50 or 1·00 g sodium butyrate/kg) with 6 replicates each. In experiment 2, 120 1-d-old chickens were fed a control diet (without sodium butyrate) or 1·00 g sodium butyrate/kg diet. Half of the chickens fed on each diet were injected intra-peritoneally with 0·5 g/kg body weight of Escherichia coli lipopolysaccharide (LPS) at 16, 18 and 20 d of age. 2. There was no effect of dietary sodium butyrate on growth performance. On d 21, serum interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) were decreased in chickens given 1·00 g sodium butyrate/kg, serum superoxide dismutase (SOD) and catalase activities were significantly increased, and malondialdehyde (MDA) was decreased by dietary sodium butyrate at 0·50 or 1·00 g/kg. On d 42, serum IL-6 was markedly decreased by dietary sodium butyrate, while 1·00 g sodium butyrate/kg greatly reduced MDA and increased catalase. 3. LPS challenge significantly reduced the growth performance of chickens. Serum IL-1β, IL-6, TNF-α, corticosterone, alpha-1 acid glycoprotein (AGP) and prostaglandin E(2) (PGE(2)) were increased in LPS-challenged chickens. Dietary sodium butyrate supplementation maintained the body weight gain and feed intake. Sodium butyrate supplementation inhibited the increase in IL-6 and AGP in serum at 16 d of age and TNF-α, corticosterone, AGP and PGE(2) at 20 d of age. Similar inhibitory effects of sodium butyrate in serum glucose and total protein concentrations were also found at 20 d of age. 4. The results indicated that dietary sodium butyrate supplementation can improve the growth performance in chickens under stress and that this may be used to moderate the immune response and reduce tissue damage.