Three experiments were conducted to evaluate the effects of chitin and protein constituents in shrimp meal (SM) on growth performance, nutrient digestibility and retention, intestinal microbial populations, immune response, volatile fatty acids and ammonia production in broilers. In addition, the effect of dietary SM on the above parameters in broilers administered with Lactobacillus spp. and Bacillus spp were also evaluated. In Experiment 1, a total of 54 eight-day-old male chicks were randomly allotted to individual cages and fed 1 of 9 diets (1 control, 4 SM and 4 purified chitin) for 28 d (with 6 replicates of each treatment). In experiment 2, one-day-old-male chicks (n=400) were randomly distributed to 5 dietary treatment groups (1 control and 4 SM: 5, 10, 15 and 20%) through 42 d of age. In experiment 3, a total of 180, one-day-old male chicks were randomly allotted to 6 treatments. On four days of age, chicks were each dosed by oral gavage into crop with 108 cells/ml of Lactobacillus spp. or Bacillus spp. Six experimental diets were as follow: 1) Control (soybean meal based protein diets) 2) SM 3) Control + Lactobacillus 4) Control + Bacillus 5) SM + Lactobacillus 6) SM + Bacillus Growth performance and DM, organic matter, ash and chitin digestibilities and nitrogen retention did not change significantly when SM was on level or below level of 15%. Feeding broilers with SM resulted in increased populations of intestinal Lactobacillus and decreased intestinal E. coli and cecal Salmonella. Moreover, SM can be decreased blood urea nitrogen and increased lysozyme and monocyte of broilers. The cecal butyric acid concentration in broilers fed SM was also significantly increased. There were no significant effects of purified chitin on any of the studied parameters. However, feeding chitin from SM and purified chitin resulted in similar effects in reducing ammonia levels. In broilers fed SM containing diets with the administration of Lactobacillus spp. Or Bacillus spp. had a lower ammonia concentration than broilers fed SM alone. In conclusion, SM can be used up to 15% in broiler diets. In addition, SM may potentially modulate intestinal microbial population changes, immune response and volatile fatty acid and ammonia production. The supplementation of Lactobacillus spp. or Bacillus spp. may improve the efficacy of SM.