The effects of live yeast (LY) on immune responses and intestinal morphological structure in lipopolysaccharide (LPS) challenged broilers were investigated. A total of 480 one-day-old male broilers were divided into six groups following a 3 × 2 factorial arrangement (eight replicates) with three dietary LY dosages (0%, 0.05%, or 0.50%) and two immune treatments (injection of saline or LPS) given at an interval of 48 h between 21 and 27 d of age. Blood was sampled on days 21 and 27, while intestine were collected on day 28. Results showed that LPS damaged (P ≤ 0.05) intestinal histomorphology, and tended to reduce (P=0.071) serum anti-Newcastle disease virus (NDV) titers on day 21, but increase (P=0.089) jejunal maltase activity. Supplemental LY at 0.05% elevated (P ≤ 0.05) ileal villus width and villus surface area, and serum anti-NDV titers on day 21. The addition at 0.50% increased (P ≤ 0.05) jejunal and ileal villus height to crypt depth ratio, reduced (P ≤ 0.05) jejunal maltase activity and crypt depth, and attenuated (P ≤ 0.05) LPS-induced increase (P ≤ 0.05) in serum diamine oxidase activity on day 21. Collectively, supplemental LY at 0.05% improved antibody response and the addition at 0.50% alleviated LPS-induced intestinal damage in broilers.