1. The objective of this study was to investigate the protective effects of a peptidoglycan produced by Limosilactobacillus reuteri against aflatoxin B 1 (AFB 1 ) induced toxicity in vitro and in vivo in broiler chicks.2. Toxin adsorption experiments were carried out firstly in vitro . These experiments indicated that the absorption efficiency of the peptidoglycan for AFB 1 was 64.3-75.9%.3. In the in vivo experiments, Hy-Line Brown chicks were fed a diet containing AFB 1 at 71.43 µg/kg with and without peptidoglycan supplementation at concentrations of 100, 200, or 300 g/kg feed from 0-42 d of age.4. The peptidoglycan supplementation in AFB 1 -contaminated diets resulted in significant improvements in terms of average daily gain, feed intake, feed conversion ratio, white blood cell count, haemoglobin content, glutathione peroxidase activity, immunoglobulin (Ig) A, IgG, IgM and Newcastle disease virus antibody titres ( p < 0.05) and diminished liver steatosis.5. In conclusion, peptidoglycan supplementation alleviated AFB 1 -induced toxicity through adsorbing toxins and improving growth performance, antioxidant ability, immunity and liver pathological changes in chicks. The optimal supplemental dose was 200 mg/kg in feed.