New 2,3-substituted-1,3-thiazolidin-4-one (6a-f) were prepared by cyclocondensation of 2-[6-(4-chlorobenzyloxy)-2-naphthyliden]-4-(4-substituted phenyl)-5-methyl-1,3-thiazole (5a-f) and mercaptoacetic acid in benzene. The synthesized compounds were characterized on the basis of elemental analysis, 1 H NMR, 13 C NMR and FT-IR. The prepared compounds have been screened in vitro against two Grampositive Staphylococcus aureus, Staphylococcus epidermidis, and two Gram-negative Escherichia coli, Pseudomonas aernuginosa for antibacterial activity and two fungal strains Candida albicans, Candida krusei for antifungal activity using ciprofloxacin, ampicillin and ketoconazole with minimal inhibitory concentration (MIC) value of 10 mcg/L in DMSO. Compounds 6a and 6d showed good antibacterial and antifungal activities compared to reference medications utilized within this study.