en ميکروب شناسي Microbiology تحقيقي Original Paper <strong>Background and objectives:</strong> Antibiotic resistance is a major public health challenge. The pervasive antibiotic misuse can lead to increased antibiotic resistance. Thus, there is a need for discovery of new compounds against drug-resistant microorganisms. We synthesized new series of 1, 3, 4-oxadiazole derivatives (4a-4d) and evaluated the antibacterial and antifungal activity of the derivatives against <em>Staphylococcus aureus</em>, <em>Staphylococcus epidermidis</em>, <em>Acinetobacter baumannii</em>, <em>Klebsiella pneumoniae</em>, <em>Aspergillus fumigatus</em> and <em>Aspergillus flavus</em>.<br> <strong>Methods:</strong> The new derivatives of 1, 3, 4-oxadiazole were synthesized using a single-stage, high-yield method. The structure of the new compounds was confirmed by infrared spectroscopy, carbon-nuclear magnetic resonance and hydrogen- nuclear magnetic resonance. Then, antibacterial and antifungal activities of the prepared derivatives (1 mg/ml) were evaluated by determining minimum inhibitory concentration and minimum bactericidal/fungicidal concentration using the agar well diffusion method.<br> <strong>Results:</strong> All synthesized compounds, especially (4d) with methoxyphenyl group, exhibited powerful antibacterial activity against the tested bacteria. However, the compounds had no antifungal effect.<br> <strong>Conclusion:</strong> Our findings indicate the antibacterial potential of the novel synthetic 1, 3, 4-oxadiazole compounds. Anti-bacterial agents,Antifungal agents,Oxadiazoles, 13 18 http://mlj.goums.ac.ir/browse.php?a_code=A-10-946-1&slc_lang=en&sid=1 Nakisa Zarrabi Ahrabi na_zarrabi@yahoo.com 100319475328460021020 100319475328460021020 No Department of Biology, Central Tehran Branch, Islamic Azad University, Tehran, Iran Ali souldozi alisouldozi@gmail.com 100319475328460021021 100319475328460021021 No Department of Chemistry, Urmia Branch, Islamic Azad University, Urmia, Iran Yasin SarveAhrabi yasin.ahrabi2016@gmail.com 100319475328460021022 100319475328460021022 Yes Department of Biology, Central Tehran Branch, Islamic Azad University, Tehran, Iran