Two new series of Mannich bases, namely, 1-(morpholino)methyl-3-(4-methylthiobenzyl)-4-(substituted arylidene)amino-1,2,4-triazol-5-thiones 3 and 1-(N-methylpiperazino)methyl-3-(4-methylthiobenzyl)-4-(substituted arylidene)amino-1,2,4-triazol-5-thiones 4 have been synthesized by a three-component Mannich reaction (MCR) involving 3-(4-methylthiobenzyl)-4-(substituted arylidene)amino-5-mercapto-1,2,4-triazoles 2, formaldehyde and morpholine/N-methylpiperazine. The newly synthesized compounds were well characterized by elemental analysis, IR, (1)H NMR and mass spectral studies. They were also screened for their antibacterial and antifungal activities against a variety of microorganisms and the results of such studies have been discussed in this article.