A new series of 2-hydrazone-thiazoline-4-ones 3a-d and 2-hydrazone-5-arylidene-thiazoline-4-ones 4a-h, 5a-f and 6a-b were synthesized starting from various thiosemicarbazones by the Hantzsch condensation with chloroacetic acid. The newly synthesized compounds were screened for their antimicrobial activity against 4 strains of bacteria: Staphylococcus aureus (ATCC 29213), Bacillus subtilis (ATCC 60511), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 10145) and one fungal strain: Candida albicans (ATCC 10231). The compounds 3a-c demonstrated a good inhibitory activity against E. coli. The results of the antifungal screening showed that the 2-hydrazon-thiazolin-4-ones 3c, 3d and 4b presented an excellent activity against Candida albicans.