Visceral leishmaniasis caused by Leishmania infantum (Kinetoplastida: Trypanosomatidae) is a major neglected tropical disease and Brazil is the responsible for most cases reported in the Americas. In this region, L. infantum is primarily transmitted by Lutzomyia longipalpis and Migonemyia migonei (França) (Diptera: Psychodidae) is considered a permissive vector. We evaluated the susceptibility of Lu. longipalpis and Mg. migonei to Beauveria bassiana and to Eucalyptus globulus (Myrtales: Myrtaceae) essential oil. A spore suspension of B. bassiana was prepared and sand flies divided into five groups: test 1 (10⁷ spores/ml of B. bassiana with E. globulus essential oil at 4 mg/ml), test 2 (10⁷ spores/ml of B. bassiana), test 3 (E. globulus essential oil at 4 mg/ml), positive control (cypermethrin 0.1%), and negative control (sterile distilled water). Scanning electron microscopy (SEM) was performed on specimens from each group. A 50% reduction was recorded in the survival time of Lu. longipalpis in test 1 and 2, where hyphal adhesion and cuticle damage were observed by SEM. No significant differences in the survival time of Mg. migonei were found, probable due to the high mortality rate observed in the negative control group, which may be a result of the greater sensitivity of this species to laboratory conditions. The results obtained herein suggest that B. bassiana may be a potential biological control agent against Lu. longipalpis, the main vector of L. infantum in the Americas.