1. This study was conducted to evaluate the protective effect of natural sodium bentonite (NaB) in the prevention of toxic effects of aflatoxins. Five hundred and twenty-eight 1-d-old Ross male broiler chickens were housed in pens (22 chickens per pen) for 42 d. There were 3 inclusion rates of NaB (0, 2.5, and 5 g/kg) and 2 of aflatoxins (0 and 3 mg/kg food). Each treatment had 4 replicates of 22 chickens. 2. All chickens treated with aflatoxin and without bentonite were adversely affected. NaB treatment at 5.0 g/kg improved body weights at 42 d of age by 31.3%, increased food intake by 23.8% and improved productive efficiency by 40.1%. Weights of liver, heart, pancreas and crop and biochemical variables were not affected by dietary NaB. However, serum phosphorous concentration was reduced by 30% compared with chickens that received aflatoxin. 3. NaB caused no adverse effects on chickens that did not receive aflatoxin. 4. It is concluded that NaB at pH 7.9 partially neutralises the effects of aflatoxins on broiler chickens when included at 5.0 g/kg in the diet.