A series of new thiazole-hydrazones (3a-3n) were synthesized, characterized, and screened for their hMAO-A and hMAO-B inhibitory activity by an in vitro fluorometric method. Selectivity indexes (SIs) were expressed as IC50 (MAO-A) / IC50 (MAO-B). Compound 3f showed promising hMAO-A inhibition with an IC50 value of 1.20 mu M and displayed a very significant SI of 0.04 towards hMAO-A. The mechanism of hMAO-A inhibition was investigated by enzyme kinetics using Lineweaver-Burk graphics. Compound 3f was further screened for its cytotoxicity by using a healthy NIH/3T3 mouse embryonic fibroblast cell line (ATCC CRL1658) and was evaluated as nontoxic at its effective concentration against hMAO-A. The ADME prediction of the compounds revealed that they may have good pharmacokinetic profiles, which is necessary for drug candidates.