In research for promising antibacterial and antifungal compounds, a series of 2-aryl 3-[1,2,4]triazol-5-yl 4-thiazolidinones 1 were synthesized by a domino reaction of 5-amino-1H-[1,2,4]triazoles 3, aromatic aldehydes, and -mercaptoacids in boiling toluene in the presence of molecular sieves 4 A°. Of the twenty novel 3-[1,2,4]triazol-5-yl 4-thiazolidinone derivatives, four compounds 2-benzo[d][1,3]dioxol-6-yl-3-[(3-morpholin-4-yl)-1H-1,2,4-triazol-5-yl)]-1,3-thiazolidin-4-one (1i), 2-(4-chlorophenyl)-5-methyl-3-[3-(4-methylpiperazin-1-yl)-1H-1,2,4-triazol-5-yl]-1,3-thiazolidin-4-one (1p), 2-benzo[d][1,3]dioxol-6-yl-3-[3-(4-methylpiperazin-1-yl)-1H-1,2,4-triazol-5-yl]-1,3-thiazolidin-4-one (1s), 2-benzo[d][1,3]dioxol-6-yl-5-methyl-3-[3-(4-methylpiperazin-1-yl)-1H-1,2,4-triazol-5-yl]-1,3-thiazolidin-4-one (1t) exhibited MICs of 4 mg/mL or less versus Mycobacterium tuberculosis. Moreover, these compounds were screened against Candida albicans. Compounds 1p, 1s gave MICs of 1 mg/mL or less, and were fungicidal. Finally, compound 1s was evaluated against an expanded fungal panel and showed good activity against Cryptococcus neoformans. In addition, compound 1s also appeared to be fungicidal against Aspergillus arrhizus, with MIC <1 mg/mL.