The effects of natural clinoptilolite (NCLI) and modified clinoptilolite (MCLI) were evaluated in broilers challenged with lipopolysaccharide (LPS) in a 21-d feeding trial. A total of 288 one-day-old chickens were allocated into three treatment groups: control, NCLI (2%) and MCLI (2%). Half of the birds from each treatment group were challenged with either 0.9% NaCl solution or LPS (250 μg/kg body weight, orally administered) at 16, 18 and 21 d of age. Before the LPS challenge, no dietary effect on bird growth performance was found (P>0.05). When LPS was orally administered, no significant changes in growth performance of broilers was found (P>0.05). However, small intestinal morphology and development, malondialdehyde (MDA) content of the jejunual and ileal mucosa, and superoxide dismutase (SOD) activity of the ileal mucosa were significantly affected (P<0.05). Supplementation with NCLI and MCLI significantly decreased the MDA contents of the jejunual and ileal mucosa and improved the SOD activity of the ileal mucosa and the development of the small intestine compared with the control group (P<0.05). The results indicated that NCLI and MCLI additions in feed had protective effects on the gut health of broilers against LPS challenge.