The aims of the current study were to investigate the prevalence of bovine brucellosis, to correlate laboratory results of serum reactive samples to the serology of animals presenting serous pouches, and to identify possible risk factors for the development of the disease. In order to do so, 1.265 bovine blood samples were collected from male and female animals bred in different counties in Maranhão state, Brazil, and in other regions of the country. The animals were slaughtered in two slaughterhouses controlled by the Federal Inspection Service (FIS), and in two others controlled by the Municipal Inspection Service (MIS), of regions such as Açailândia and Imperatriz. Samples were tested for specific antibodies by using buffered acidified antigen (BAA) and 2-mercaptoethanol in combination with slow serum agglutination (2-ME + SSA). Additionally, an epidemiological questionnaire was applied to 100 owners, who provided animals to the slaughterhouses, to enable investigating the risk factors for bovine brucellosis. Fifteen serous pouches of animals presenting this lesion were also collected at slaughter time. Thirty-nine out of the analyzed samples were reacted to BAA, whereas 15 reacted to the 2-ME + SSA test; only one male was reagent and it resulted in 1.19% prevalence. One out of the 15 collected serous pouches reacted to the 2-ME + SSA test. The risk factors identified in this study were: the incidence of miscarriages, the sale of animals without previous examination, and the failure in testing the animals before introducing them in herds and before slaughter. It was possible to conclude that the animals slaughtered in the herein evaluated slaughterhouses were infected with Brucella abortus, as well as that this infection prevailed in females.