ABSTRACT. Dias G.E.A., de Carvalho B.O., Medeiros, P.T. deM., Sousa F.D.deR., Gomes A.V.daC., de Souza M.M.S. & de Lima C.A.R. [Oregano (Origanum vulgare L.) essential oil in the diet of broilers as balancing the intestinal microbiota.] Óleo essencial de orégano (Origanum vulgare L.) na dieta de frangos de corte como equilibrador da microbiota intestinal. Revista Brasileira de Medicina Veterinária, 37(2):108-114, 2015. Programa de Pós-Graduação em Zootecnia, Instituto de Zootecnia, Universidade Federal Rural do Rio de Janeiro, Campus Seropédica, BR 465, Km 7, Seropédica, RJ 23890-000, Brasil. E-mail: firstname.lastname@example.org The effectiveness of the use of oregano essential oil as an zootechnical additive in broiler diets was evaluated. 300 male broiler chickens were distributed in delineation in blocks at random, five treatments and six repetitions of 10 birds. The treatments consisted of diets with different levels of oregano essential oil (300, 600 and 900 mg/kg ration), a negative control (with no antimicrobial) and a positive control with the antibiotic colistin sulfate. Samples were collected from the ileum at 40 days of age with the objective of determining the count of total coliform and identifying enterobacteria. The digestibility assay was constituted of 8 adaptation days to the diet and 4 days for collecting. There was reduction (P<0.05) at the count of total coliform in chickens treated with antibiotic or oregano. There were no differences between treatments in dry matter apparent metabolization coefficients, apparent metabolizable energy and apparent metabolizable energy corrected by nitrogen balance. The treatment with higher level of oregano resulted at a higher nitrogen apparent metabolization coefficient. The oregano essential oil may be utilized in diets of broilers as zootechnical additive balancing the intestinal microbiota.