2-{3-(4-Substitutedbenzyl)-4-[2-(1H-indol-3-yl) ethyl]-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N'-(arylmethylene) acetohydrazides (5a-g), 4-amino-2-{3-(4-substitutedbenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N'-(arylmethylene) acetohydrazides (6a,b), and 4-[2-(1H-indol-3-yl) ethyl]-5-(4-substitutedbenzyl)-2-{[5-(phenylamino)-1,3,4-thiadiazol-2-yl] methyl}-2,4-dihydro-3H-1,2,4-triazol-3-ones (8a,b) were synthesized starting from 4-alkyl-5-(4-substitutedbenzyl)-2,4-dihydro-3H-1,2,4-triazol-3-ones (2a-c) by several steps and their structures were well characterized by elemental analyses, IR, (1)H-NMR, (13)C-NMR, and mass spectral studies. They were also screened for their microbial activities. The obtained antimicrobial activity results revealed that 12 among the 24 compounds tested displayed variable growth inhibition effects on the tested gram-positive and gram-negative bacterial strains. None of the compounds showed antifungal activity against yeast-like fungi.