The aim of this study was to investigate the susceptibility in vitro of Trypanosoma evansi to the essential oils of andiroba (Carapa guianensis) and aroeira (Schinus molle), in their conventional and nanostructured forms. For that, pure oils at concentrations of 0.5, 1.0 and 2.0% were used. A negative control (untreated) and a positive control (diminazene aceturate 0.5%) were used as comparative parameters. Later, the same tests were performed, using nanoemulsions oils at concentrations of 0.5 and 1.0%. The tests were carried out in triplicates and the numbers of parasites were quantified on 1, 3 and 6 hours from onset of the study. A dose-dependent reduction in the number of parasites to the forms of two oils tested was observed after 1 hour. The concentration of parasites was significantly reduced at low concentrations after 3 hours, as well as at 6 hours no alive parasites were observed for the essential oils tested. Ours findings indicate, for the first time, that oils of andiroba and aroeira (in their conventional and nanoemulsion forms) have high activity against T. evansi in vitro, leading to the suggestion that these oils may be applied as an alternative treatment for this disease.