Through a cyclization reaction of 2-phenylbutyric acid with N-phenylthiosemicarbazide and POCl3, novel 1,3,4-thiadiazole derivatives were synthesized. Their structures were confirmed using IR, H-1 NMR, and C-13 NMR spectroscopies and elemental analysis. The antibacterial activities of the obtained 1,3,4-thiadiazole derivatives were tested against Gram-negative bacteria (Salmonella enteritidis, Salmonella typhimurium, Enterobacter aerogenes, Salmonella infantis, Salmonella kentucky, and Escherichia coli) and Grampositive bacteria (Staphylococcus aureus, Bacillus subtilis, and Enterococcus durans) using a disk diffusion method. Moreover, an antifungal activity experiment was performed against Candida albicans using the disk diffusion method. It was observed that the synthesized 1,3,4-thiadiazole derivatives exhibited effective antimicrobial activity against S. aureus, E. coli, and C. albicans. Based on these results, the 1,3,4-thiadiazole derivatives can be considered as a source of bioactive agents for pharmacological and medicinal applications.