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Aeriscardovia aeriphila , also known as Bifidobacterium aerophilum , was first isolated from the caecal contents of pigs and the faeces of cotton-top tamarin. Bifidobacterium species play important roles in preventing intestinal infections, decreasing cholesterol levels, and stimulating the immune system. In this study, we isolated a strain of bacteria from the duodenal contents of broiler chickens, which was identified as A. aeriphila , and then evaluated the effects of A. aeriphila on growth performance, antioxidant functions, immune functions, and gut microbiota in commercial broiler chickens. Chickens were orally gavaged with A. aeriphila (1×10 9 CFU/mL) for 21 d. The results showed that A. aeriphila treatment significantly increased the average daily gain and reduced the feed conversion ratio ( P <0.001). The levels of serum growth hormone (GH) and insulin-like growth factor 1 (IGF-1) were significantly increased following A. aeriphila treatment ( P <0.05). Blood urea nitrogen and aspartate aminotransferase levels were decreased, whereas glucose and creatinine levels increased as a result of A. aeriphila treatment. Furthermore, the levels of serum antioxidant enzymes, including catalase ( P <0.01), superoxide dismutase ( P <0.001), and glutathione peroxidase ( P <0.05), and total antioxidant capacity ( P <0.05) were enhanced following A. aeriphila treatment. A. aeriphila treatment significantly increased the levels of serum immunoglobulin A (IgA) ( P <0.05), IgG ( P <0.01), IgM ( P <0.05), interleukin-1 (IL-1) ( P <0.05), IL-4 ( P <0.05), and IL-10 ( P <0.05). The broiler chickens in the A. aeriphila group had higher secretory IgA (SIgA) levels in the duodenum ( P <0.01), jejunum ( P <0.001), and cecum ( P <0.001) than those in the control group. The messenger RNA (mRNA) relative expression levels of IL-10 ( P <0.05) and IL-4 ( P <0.001) in the intestinal mucosa of chickens were increased, while nuclear factor-‍κB ( NF ‍ - ‍ κB ) ( P <0.001) expression was decreased in the A. aeriphila group compared to the control group. Phylum-level analysis revealed Firmicutes as the main phylum, followed by Bacteroidetes, in both groups. The data also found that Phascolarctobacterium and Barnesiella were increased in A. aeriphila -treated group. In conclusion, oral administration of A. aeriphila could improve the growth performance, serum antioxidant capacity, immune modulation, and gut health of broilers. Our findings may provide important information for the application of A. aeriphila in poultry production.