Previous studies have demonstrated that Lactobacillus has anti-inflammatory properties, but the protective functions of Lactobacillus and mechanisms of inhibition of necrotic enteritis (NE) in the intestines of chickens have not been fully clarified. In the present study, we selected a probiotic strain, Lactobacillus fermentum 1.2029, which has good adhesive ability and a high survival rate in low pH and bile salts. The objective of this study was to examine the anti-inflammatory properties of L. fermentum 1.2029 against NE in chickens. Two hundred forty 1-d-old male Arbor Acres broilers were blocked into 3 experimental groups as follows: (I) nonchallenge control group, (II) Clostridium perfringens challenge group, and (III) C. perfringens challenge + L. fermentum 1.2029 group. Lactobacillus fermentum 1.2029 (1.0 mL/d, 10(8) cfu/mL) was orally administered daily to group III during the course of the experiment, and all uninfected control chickens were inoculated accordingly with the same volume of PBS. Clostridium perfringens (0.5 mL on d 1 and 1.0 mL on d 14 to 21, 10(8) cfu/mL) was administered to chickens in group II. At 28 d, scoring of gross NE lesions was performed. Ileal segments of approximately 2 cm from 24 chickens in each experimental group were collected and fixed in 4% (wt/vol) neutral-buffered formalin solution for histological scoring. Ileal mucosa samples were also collected for mRNA analysis by real-time PCR. The results showed that L. fermentum 1.2029 reduced the severity of NE lesions in chickens. Histological scores revealed that L. fermentum 1.2029 also reduced the inflammation damage of NE in chickens. Changes in cytokines and Toll-like receptors (TLR) were determined, and L. fermentum 1.2029 was found to increase interleukin-10 levels and reduce interferon-γ and TLR2 levels in NE-infected chickens. The results showed that L. fermentum 1.2029 was able to regulate the intestinal mucosal immune response and ameliorate inflammation by changing expression levels of cytokines and TLR.