The effect of a Lactobacillus plantarum-supplemented diet on shrimp growth, digestive tract bacterial microbiota, survival, and some hemato-immunological parameters after an experimental challenge with Vibrio harveyi was studied. No difference (P>0.05) was observed in shrimp survival (80±6%) and final weight (6.63±0.56g) after 60 days feeding trial. Total bacteria count and Vibrio spp. count in the digestive tract were not diferent (P>0.05) until day 40, but they were lower (P<0.05) in the probiotic-supplemented group on day 60. Total lactic bacteria in the shrimp digestive tract was higher after day 20 in the probiotic-supplemented group. Ten hours after V. harveyi challenge, survival of the probiotic-supplemented group (65.7±2.9%) was higher (P>0.05) than the control group (39.9±4.4%). Bacterial counts in hemolymph and hepatopancreas was lower (P<0.05) in the probiotic-supplemented group than in the control group after V. harveyi challenge. Total hemocyte count and serum agglutination activity were higher (P>0.05) in the probiotic-supplemented group after challenge with V. harveyi. Probiotic-supplemented diet modifies shrimp digestive tract bacterial microbiota, increasing resistance to V. harveyi infection. Keywords: Litopenaeus vannamei, Lactobacillus plantarum, intestinal microbiota, immunostimulation RESUMO Avaliou-se o efeito de uma dieta suplementada com Lactobacillus plantarum na engorda de