Technical Abstract: Coccidiosis is the major parasitic disease of poultry and is caused by the apicomplexan parasites Eimeria. Drugs and live vaccines are the two main control measures of the disease; however, due to increasing concerns with prophylactic drug use and high cost of vaccines, alternative control methods are needed. Recent evidence that various dietary and live microbial supplements can influence host immunity against enteric diseases prompted us to investigate the role of a Pediococcus-based probiotic on coccidiosis in broiler chickens. In the present study, we examined body weight gains, oocyst shedding, and antibody responses of broilers fed the commercial probiotic MitoGrow' (MG). Day-old chicks were fed either a regular broiler diet (REG) or one of two probiotic diets supplemented with 0.1% (MG 0.1) or 0.2% (MG 0.2) of MitoGrow. Chicks were orally challenged with 5,000 or 10,000 sporulated oocysts of Eimeria acervulina (EA) or with 5,000 Eimeria tenella (ET) oocysts on days 10 or 12 of age, respectively. In EA-infected birds, 0.1% MitoGrow improved (P < 0.05) weight gain as compared to the other two groups, and reduced (P < 0.05) oocyst shedding in birds infected with 5,000 EA oocysts. In ET-infected birds, Eimeria-specific antibody levels were higher (P < 0.05) in the MitoGrow-fed groups, especially in MG 0.1 birds, compared to the regular diet group though their oocyst shedding and weight gains were not clearly improved. These results demonstrate that this Pediococcus acidilactici-based probiotic effectively enhances the resistance of birds and partially protects against the negative growth effects associated with coccidiosis, particularly when supplemented at 0.1% of the diet.