Since molecules containing 1,3,4-oxadiazoles and 1,2,4-triazole heterocyclic rings in their structures have important biological activities; 5-(4-Bromobenzyl)-4-(4-(5-phenyl-1,3,4-oxadiazole-2-yl)phenyl)-2,4-dihydro-3H-1,2,4-triazole-3-one (II) was synthesized, the synthesized compound was characterized by using NMR and IR spectroscopic methods. HOMO and LUMO energies, geometrical structure parameters, IR parameters and NMR chemical shift values were calculated by using DFT method. IR and NMR experimental values were compared with DFT results. Due to the differences between experimental IR and NMR spectral values and theoretical ones, N-H center dot center dot center dot O type intermolecular strong hydrogen bond was recommended. Antimicrobial activities of the synthesized compound II was determined against fifteen different bacteria and the Leishmania major species by microdilution broth assay with Alamar Blue Dye. Compound II was found to be low effective on three different bacterial species (Minimum Inhibitory Concentration (MIC):5000 mu g/ml) and had the high antileishmanial activity (MIC: 1250 mu g/mL). In order to use the synthesized compound as a drug candidate, control studies should be performed in experimental animal models in vivo. (C) 2020 Published by Elsevier B.V.