Abstract Some novel 3-alkyl(aryl)-4-(3-acetoxy-4-methoxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4a-h) were synthesized from the rections of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2a-h) with 3-acetoxy-4-methoxybenzaldehyde (3). The new eight compounds were characterized using by elemental analyses and IR, 1H-NMR, 13C-NMR and UV spectral data. In addition, the synthesized compounds were analyzed for their in vitro potential antioxidant activities in three different methods. Antibacterial activity of the compounds 4a-h were also evaluated aginst six bacteria such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus and Klebsiella pneumoniae. Moreover, 4 type compounds were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as isopropyl alcohol, tert-butyl alcohol, acetone, N,N-dimethylformamide and the half-neutralization potential values and the corresponding pKa values were determined for all cases.